Date and time procedures. More...

Functions/Subroutines
subroutine	set_date_and_time (year, month, day, hour, minute, second)
	Set global date/time variables (year, month, ..., minute, second in TheSky_local) to specified values.

subroutine	get_date_and_time (year, month, day, hour, minute, second)
	Retrieve the current global date/time variables (year, month, ..., minute, second, stored in TheSky_local)

subroutine	set_date_and_time_to_system_clock (ut)
	Set global date/time variables (year, month, ..., minute, second in TheSky_local) to system clock.

subroutine	ut2lt_ymdhms (year, month, dy, hour, minute, second, tz, tz0, dsttp)
	Convert date/time in ymdhms from UT to local time.

subroutine	set_date_and_time_to_jd2000 ()
	Set global date/time variables (year, month, ..., minute, second in TheSky_local) to JD2000.0.

subroutine	calctime (ut, jd, jde)
	Compute UT, JD, JDE, DeltaT and TZ, using the date and (local) time and TZ stored in the module TheSky_local.

real(double) function	calc_gmst (jd, deltat)
	Calculate Greenwich Mean Sidereal Time for any instant, in radians.

real(double) function	gmst_meeus (jd)
	Calculate Greenwich Mean Sidereal Time for any instant, in radians, using Meeus.

subroutine	localtime2jd (jd)
	Computes JD, DeltaT and TZ, from date/time variables in module TheSky_local.

real(double) function	calc_deltat (jd, force_recompute)
	Compute DeltaT for a given JD.

real(double) function	calc_deltat_ymd (y, m, d, force_recompute)
	Compute DeltaT for given y,m,d.

real(double) function	find_deltat_in_range (y, y0)
	Find a precise value for DeltaT through linear interpolation of the two adjacent tabulated values.

real(double) function	calc_deltat_approx (jd)
	Compute DeltaT for given JD, using a simple parabolic approximation.

subroutine	jd2dtm (jd, yy, mm, d, h, m, s)
	Convert a Julian day (UT) to LOCAL date and time (h,m,s)

subroutine	jd2dthm (jd, yy, mm, d, h, m)
	Convert a Julian day (UT) to LOCAL date and time (h,m - no seconds)

real(double) function	jd2ltime (jd0)
	Convert a Julian day (UT) to a local time (LT, h)

subroutine	printdate (jd, jde)
	Prints date/time of a given Julian day (UT) to standard output.

subroutine	printdate1 (jd, jde)
	Prints date/time of a given Julian day (UT) to standard output, but without a newline.

subroutine	dls (yr, jdb, jde)
	Find the two Julian days of the beginning and the end of daylight-savings time in the EU for a given year.

real(double) function	gettz (jd, tz0, dsttp)
	Returns time zone: tz0 (standard time) or tz0+1 (daylight-savings time)

subroutine	print_date_time_and_location (op, nlbef, nlaf, ut, jd, jde, locname, tzname)
	Display a banner with date, time and location of calculation. Computes and returns UT, JD and JDE.

integer function	dow (jd0)
	Calculates day of week (0 - Sunday, ..., 6=Saturday)

integer function	woy (jd)
	Calculate the week-of-year number.

subroutine	easter_gauss (year, month, day)
	Calculate the date of Easter using Gauss' method.

subroutine	passover_gauss (year, month, day)
	Calculate the date of Passover or Pesach (Jewish Easter) using Gauss' method.

Detailed Description

Date and time procedures.

Function/Subroutine Documentation

◆ calc_deltat()

real(double) function thesky_datetime::calc_deltat	(	real(double), intent(in)	jd,
		logical, intent(in), optional	force_recompute )

Compute DeltaT for a given JD.

Parameters

jd	Julian day
force_recompute	Force recomputation of DeltaT, even if the year is the same as in the last call (done in calc_deltat_ymd())

Return values

calc_deltat Delta T (s)

Note: VERY SLOW, use calc_deltat_ymd() if y,m,d are known

Definition at line 351 of file date_time.f90.

References calc_deltat(), calc_deltat_ymd(), thesky_local::day, thesky_constants::deltat_forced, thesky_local::month, and thesky_local::year.

Referenced by calc_deltat(), thesky_planets::jupiterphys(), thesky_moon::moonpos_la(), thesky_planets::planet_position(), thesky_planets::planetelements(), and thesky_sun::sunpos_la().

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◆ calc_deltat_approx()

real(double) function thesky_datetime::calc_deltat_approx ( real(double), intent(in) jd )

Compute DeltaT for given JD, using a simple parabolic approximation.

Parameters

jd	Julian day for computation

Return values

deltat The value for DeltaT (= TDT-UT) in seconds.

Definition at line 520 of file date_time.f90.

References calc_deltat_approx(), and thesky_constants::jd1820.

Referenced by calc_deltat_approx().

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◆ calc_deltat_ymd()

real(double) function thesky_datetime::calc_deltat_ymd	(	integer, intent(in)	y,
		integer, intent(in)	m,
		real(double), intent(in)	d,
		logical, intent(in), optional	force_recompute )

Compute DeltaT for given y,m,d.

Parameters

y	Year
m	Month
d	Day
force_recompute	Force recomputation of DeltaT, even if the year is the same as in the last call

Return values

calc_deltat_ymd Delta T (s)

Note

Faster than calc_deltat. Use this routine rather than calc_deltat() if y,m,d are known

Definition at line 407 of file date_time.f90.

References calc_deltat_ymd(), thesky_constants::deltat_0, thesky_constants::deltat_accel, thesky_constants::deltat_change, thesky_constants::deltat_forced, thesky_constants::deltat_maxyr, thesky_constants::deltat_minyr, thesky_constants::deltat_values, thesky_constants::deltat_years, and find_deltat_in_range().

Referenced by calc_deltat(), calc_deltat_ymd(), calctime(), and localtime2jd().

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◆ calc_gmst()

real(double) function thesky_datetime::calc_gmst	(	real(double), intent(in)	jd,
		real(double), intent(in), optional	deltat )

Calculate Greenwich Mean Sidereal Time for any instant, in radians.

Parameters

jd	Julian day of computation
DeltaT	ΔT (s) (optional - default: use DelTaT from TheSky_local)

Return values

calc_gmst Greenwich Mean Sidereal Time (radians)

See also: Explanatory Supplement to the Astronomical Almanac, 3rd edition, Eq. 6.66 (2012)

Definition at line 252 of file date_time.f90.

References calc_gmst(), and thesky_local::deltat.

Referenced by calc_gmst(), thesky_visibility::limmag_zenith_jd(), thesky_moon::moonpos_la(), thesky_planets::planet_position(), print_date_time_and_location(), and thesky_sun::sunpos_la().

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◆ calctime()

subroutine thesky_datetime::calctime	(	real(double), intent(out)	ut,
		real(double), intent(out)	jd,
		real(double), intent(out)	jde )

Compute UT, JD, JDE, DeltaT and TZ, using the date and (local) time and TZ stored in the module TheSky_local.

Parameters

ut	Universal time (output)
jd	Julian date (output)
jde	Julian date (output)

Note

Date and time are obtained from year, month, day, hour, minute, second, through the module TheSky_local, assuming LOCAL time
DeltaT and TZ are returned through the module TheSky_local
Computed JD is in UNIVERSAL time

Todo: Remove recomputation of 'UT JD'!!!

Definition at line 212 of file date_time.f90.

References calc_deltat_ymd(), thesky_local::day, thesky_local::deltat, gettz(), thesky_local::hour, thesky_local::minute, thesky_local::month, thesky_local::second, thesky_local::tz, and thesky_local::year.

Referenced by print_date_time_and_location().

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◆ dls()

subroutine thesky_datetime::dls	(	integer, intent(in)	yr,
		real(double), intent(out)	jdb,
		real(double), intent(out)	jde )

Find the two Julian days of the beginning and the end of daylight-savings time in the EU for a given year.

Parameters

yr	Year (CE)
jdb	Julian day of beginning of DST (output)
jde	Julian day of end of DST (output)

Definition at line 777 of file date_time.f90.

References dow().

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◆ dow()

integer function thesky_datetime::dow ( real(double), intent(in) jd0 )

Calculates day of week (0 - Sunday, ..., 6=Saturday)

Parameters

jd0	Julian day (UT)

Return values

dow	The day of week (0=Sunday, ..., 6=Saturday)

Note: Input in UT, output in local time

Todo: Switch using dow(jd) to dow_ut(jd+tz/24.d0) to make it general

Definition at line 1006 of file date_time.f90.

References dow(), and thesky_local::tz.

Referenced by dls(), dow(), gettz(), print_date_time_and_location(), and woy().

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◆ easter_gauss()

subroutine thesky_datetime::easter_gauss	(	integer, intent(in)	year,
		integer, intent(out)	month,
		integer, intent(out)	day )

Calculate the date of Easter using Gauss' method.

Parameters

year	Julian/Gregorian year to compute date of Easter for.
month	Julian/Gregorian month of year of Easter Sunday.
day	Julian/Gregorian day of month of Easter Sunday.

Note

Based on Gauß, C.F., 1816. Berichtigung zu dem Aufsatze: Berechnung des Osterfestes. Zeitschrift für Astronomie und verwandte Wissenschaften, Bd, 1, p.158.
Taken from https://en.wikipedia.org/wiki/Date_of_Easter

Definition at line 1062 of file date_time.f90.

◆ find_deltat_in_range()

real(double) function thesky_datetime::find_deltat_in_range	(	integer, intent(in)	y,
		real(double), intent(in)	y0 )

Find a precise value for DeltaT through linear interpolation of the two adjacent tabulated values.

Parameters

y	Current year
y0	Current date, as fractional year

Return values

find_deltat_in_range Delta T (s)

Definition at line 485 of file date_time.f90.

References thesky_constants::deltat_n, thesky_constants::deltat_values, thesky_constants::deltat_years, and find_deltat_in_range().

Referenced by calc_deltat_ymd(), and find_deltat_in_range().

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◆ get_date_and_time()

subroutine thesky_datetime::get_date_and_time	(	integer, intent(out)	year,
		integer, intent(out)	month,
		integer, intent(out)	day,
		integer, intent(out)	hour,
		integer, intent(out)	minute,
		real(double), intent(out)	second )

Retrieve the current global date/time variables (year, month, ..., minute, second, stored in TheSky_local)

Parameters

year	Year (output)
month	Month (output)
day	Day (output)
hour	Hour (output)
minute	Minute (output)
second	Second (output)

Definition at line 97 of file date_time.f90.

References thesky_local::day, thesky_local::hour, thesky_local::minute, thesky_local::month, thesky_local::second, and thesky_local::year.

◆ gettz()

real(double) function thesky_datetime::gettz	(	real(double), intent(in)	jd,
		real(double), intent(in), optional	tz0,
		integer, intent(in), optional	dsttp )

Returns time zone: tz0 (standard time) or tz0+1 (daylight-savings time)

Parameters

jd	Julian day (UT?)
tz0	Default time zone for the current location ('winter time')
dsttp	Daylight-savings time rules to use: 0: no DST (e.g. UT), 1: EU, 2: USA/Canada

Return values

gettz The time zone (h; positive east of Greenwich)

Note

currently only implemented for no DST (dsttp=0), EU (dsttp=1) and USA/Canada >2007 (dsttp=2)
tz0 and dsttp can be provided through the module TheSky_local, or using the optional arguments. Note that using the latter will update the former!

Definition at line 820 of file date_time.f90.

References dow(), thesky_local::dsttp, gettz(), thesky_local::tz, and thesky_local::tz0.

Referenced by thesky_riset::best_obs_date(), thesky_visibility::best_planet_xsmag(), calctime(), gettz(), localtime2jd(), print_date_time_and_location(), and ut2lt_ymdhms().

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◆ gmst_meeus()

real(double) function thesky_datetime::gmst_meeus ( real(double), intent(in) jd )

Calculate Greenwich Mean Sidereal Time for any instant, in radians, using Meeus.

Parameters

jd	Julian day of computation

Return values

gmst_meeus Greenwich Mean Sidereal Time in radians

See also: Meeus, Sect. 12: Siderial time at Greenwich; Eq.12.4

Definition at line 287 of file date_time.f90.

References gmst_meeus().

Referenced by gmst_meeus().

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◆ jd2dthm()

subroutine thesky_datetime::jd2dthm	(	real(double), intent(in)	jd,
		integer, intent(out)	yy,
		integer, intent(out)	mm,
		integer, intent(out)	d,
		integer, intent(out)	h,
		integer, intent(out)	m )

Convert a Julian day (UT) to LOCAL date and time (h,m - no seconds)

Parameters

jd	Julian day (UT)
yy	Year (CE, LT) (output)
mm	Month (LT) (output)
d	Day (LT) (output)
h	Hour (LT) (output)
m	Minute (LT) (output)

Definition at line 616 of file date_time.f90.

References thesky_local::tz.

◆ jd2dtm()

subroutine thesky_datetime::jd2dtm	(	real(double), intent(in)	jd,
		integer, intent(out)	yy,
		integer, intent(out)	mm,
		integer, intent(out)	d,
		integer, intent(out)	h,
		integer, intent(out)	m,
		real(double), intent(out)	s )

Convert a Julian day (UT) to LOCAL date and time (h,m,s)

Parameters

jd	Julian day (UT)
yy	Year (CE, LT) (output)
mm	Month (LT) (output)
d	Day (LT) (output)
h	Hour (LT) (output)
m	Minute (LT) (output)
s	Second (+ fraction, LT) (output)

Definition at line 547 of file date_time.f90.

References thesky_local::tz.

◆ jd2ltime()

real(double) function thesky_datetime::jd2ltime ( real(double), intent(in) jd0 )

Convert a Julian day (UT) to a local time (LT, h)

Parameters

jd0	Julian day (UT)

Return values

jd2ltime Local time (h)

Definition at line 674 of file date_time.f90.

References jd2ltime(), and thesky_local::tz.

Referenced by jd2ltime().

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◆ localtime2jd()

subroutine thesky_datetime::localtime2jd ( real(double), intent(out) jd )

Computes JD, DeltaT and TZ, from date/time variables in module TheSky_local.

Parameters

JD	Julian date (output)

Note

Date and time are obtained from year, month, day, hour, minute, second, through the module TheSky_local
DeltaT and TZ are returned through the module TheSky_local

Definition at line 317 of file date_time.f90.

References calc_deltat_ymd(), thesky_local::day, thesky_local::deltat, gettz(), thesky_local::hour, thesky_local::minute, thesky_local::month, thesky_local::second, thesky_local::tz, and thesky_local::year.

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◆ passover_gauss()

subroutine thesky_datetime::passover_gauss	(	integer, intent(in)	year,
		integer, intent(out)	month,
		integer, intent(out)	day )

Calculate the date of Passover or Pesach (Jewish Easter) using Gauss' method.

Parameters

year	Julian/Gregorian year to compute date of Passover for.
month	Julian/Gregorian month of year of the DAY of Passover.
day	Julian/Gregorian day of month of the DAY of Passover.

Note

Based on Gauss, C.F., 1802. Berechnung des Judischen Osterfestes. Werke, pp.80-81, as described in Meeus, Ch.9.
Passover is always on 15 Nisan. Note that this is the DAY of Passover, the day AFTER the evening of the (first) Seder.
Valid for the Julian and Gregorian calendar.
The Jewish year is the Julian/Gregorian year + 3760.
For the years -4000 - +4000, this corresponds EXACTLY to Har’El, Z., 2005. Gauss Formula for the Julian Date of Passover. A∆(A), 1, p.0. Har’El also computes the day of week, which for the same years corresponds exactly to dow(cal2jd(year,month,day)) with cal2jd from libSUFR/date_and_time, dow() from libTheSky/datetimeSky, and year,month,day as in the current subroutine. Note that Passover day can only fall on Sun, Tue, Thu or Sat.

Definition at line 1124 of file date_time.f90.

◆ print_date_time_and_location()

subroutine thesky_datetime::print_date_time_and_location	(	integer, intent(in), optional	op,
		integer, intent(in), optional	nlbef,
		integer, intent(in), optional	nlaf,
		real(double), intent(out), optional	ut,
		real(double), intent(out), optional	jd,
		real(double), intent(out), optional	jde,
		character, dimension(*), intent(in), optional	locname,
		character, dimension(*), intent(in), optional	tzname )

Display a banner with date, time and location of calculation. Computes and returns UT, JD and JDE.

Parameters

op	Output unit (optional, default 6)
nlbef	Number of newlines before output (optional, default 0)
nlaf	Number of newlines after output (optional, default 0)
ut	UT: Universal Time (optional)
jd	JD: Julian day (optional)
jde	JDE: Apparent Julian day (optional)
locname	Location name (optional)
tzname	Time-zone name (optional)

Note

uses the module local to obtain the variables year, month, etc.
calls calctime(), gettz()

Definition at line 932 of file date_time.f90.

References calc_gmst(), calctime(), thesky_local::day, thesky_local::deltat, dow(), gettz(), thesky_local::height, thesky_local::hour, thesky_local::lat0, thesky_local::lon0, thesky_local::minute, thesky_local::month, thesky_local::second, thesky_local::tz, and thesky_local::year.

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◆ printdate()

subroutine thesky_datetime::printdate	(	real(double), intent(in)	jd,
		real(double), intent(in), optional	jde )

Prints date/time of a given Julian day (UT) to standard output.

Parameters

jd	Julian day (UT)
jde	Julian day ephemeris time (dynamical time)

Note

calls printdate1()

Definition at line 706 of file date_time.f90.

References printdate1().

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◆ printdate1()

subroutine thesky_datetime::printdate1	(	real(double), intent(in)	jd,
		real(double), intent(in), optional	jde )

Prints date/time of a given Julian day (UT) to standard output, but without a newline.

Parameters

jd	Julian day (UT)
jde	Julian day ephemeris time (dynamical time)

Definition at line 728 of file date_time.f90.

Referenced by thesky_moonroutines::moon_phase_next(), and printdate().

◆ set_date_and_time()

subroutine thesky_datetime::set_date_and_time	(	integer, intent(in)	year,
		integer, intent(in)	month,
		integer, intent(in)	day,
		integer, intent(in)	hour,
		integer, intent(in)	minute,
		real(double), intent(in)	second )

Set global date/time variables (year, month, ..., minute, second in TheSky_local) to specified values.

Parameters

year	Year
month	Month
day	Day
hour	Hour
minute	Minute
second	Second

Definition at line 66 of file date_time.f90.

References thesky_local::day, thesky_local::hour, thesky_local::minute, thesky_local::month, thesky_local::second, and thesky_local::year.

Referenced by set_date_and_time_to_jd2000().

◆ set_date_and_time_to_jd2000()

subroutine thesky_datetime::set_date_and_time_to_jd2000

Set global date/time variables (year, month, ..., minute, second in TheSky_local) to JD2000.0.

Definition at line 188 of file date_time.f90.

References set_date_and_time().

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◆ set_date_and_time_to_system_clock()

subroutine thesky_datetime::set_date_and_time_to_system_clock ( logical, intent(in), optional ut )

Set global date/time variables (year, month, ..., minute, second in TheSky_local) to system clock.

Parameters

ut	Return UT instead of local system time (optional).

Definition at line 123 of file date_time.f90.

References thesky_local::day, thesky_local::hour, thesky_local::minute, thesky_local::month, thesky_local::second, thesky_local::tz, and thesky_local::year.

◆ ut2lt_ymdhms()

subroutine thesky_datetime::ut2lt_ymdhms	(	integer, intent(inout)	year,
		integer, intent(inout)	month,
		integer, intent(inout)	dy,
		integer, intent(inout)	hour,
		integer, intent(inout)	minute,
		real(double), intent(inout)	second,
		real(double), intent(out)	tz,
		real(double), intent(in)	tz0,
		integer, intent(in)	dsttp )

Convert date/time in ymdhms from UT to local time.

Parameters

year	Year CE: input: UT, output: LT (I/O)
month	Month of year: input: UT, output: LT (I/O)
dy	Day of month: input: UT, output: LT (I/O)
hour	Hour of day: input: UT, output: LT (I/O)
minute	Minute of time: input: UT, output: LT (I/O)
second	Second of time: input: UT, output: LT (I/O)
tz	Timezone of date (output)
tz0	Default timezone for date/time
dsttp	Timezone type for date/time

Definition at line 162 of file date_time.f90.

References gettz().

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◆ woy()

integer function thesky_datetime::woy ( real(double), intent(in) jd )

Calculate the week-of-year number.

Parameters

jd	Julian day

Return values

woy	Week number in the year

Todo

CHECK: int or floor?
Depends on dow(), which depends on module local -> switch to dow_ut()

Definition at line 1033 of file date_time.f90.

References dow(), and woy().

Referenced by woy().

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Functions/Subroutines

Detailed Description

Function/Subroutine Documentation

◆ calc_deltat()

◆ calc_deltat_approx()

◆ calc_deltat_ymd()

◆ calc_gmst()

◆ calctime()

◆ dls()

◆ dow()

◆ easter_gauss()

◆ find_deltat_in_range()

◆ get_date_and_time()

◆ gettz()

◆ gmst_meeus()

◆ jd2dthm()

◆ jd2dtm()

◆ jd2ltime()

◆ localtime2jd()

◆ passover_gauss()

◆ print_date_time_and_location()

◆ printdate()

◆ printdate1()

◆ set_date_and_time()

◆ set_date_and_time_to_jd2000()

◆ set_date_and_time_to_system_clock()

◆ ut2lt_ymdhms()

◆ woy()