dc_date_generic Module Reference

Interface declarations for procedures provided from dc_date. More...

Data Types
interface	dcdatetimecreate
interface	dcdifftimecreate
interface	dcdatetimeputline
interface	dcdifftimeputline
interface	setcaltype
interface	setsecofday
interface	validcaltype
interface	validzone
interface	zonetodiff
interface	parsetimeunits
interface	setzone
interface	eval
interface	evalday
interface	evalhour
interface	evalmin
interface	evalsec
interface	evalnondim
interface	evalsclsec
interface	evalbyunit
interface	tochar
interface	tocharcal
interface	operator(+)
interface	operator(-)
interface	operator(*)
interface	operator(/)
interface	mod
interface	operator(==)
interface	operator(>)
interface	operator(<)
interface	operator(>=)
interface	operator(<=)
interface	max
interface	min
interface	create
interface	putline

Detailed Description

Interface declarations for procedures provided from dc_date.

Author

Yasuhiro MORIKAWA, Eizi TOYODA

Copyright

Copyright (C) GFD Dennou Club, 2000-2026. All rights reserved.
License is BSD-2-Clause. see COPYRIGHT in detail

This module provides interface declarations for procedures in dc_date. See dc_date for module overview.

Procedures List

The following procedures operate on DC_DATETIME or DC_DIFFTIME derived types (which store date/time information).

Procedure	Description
DCDateTimeCreate	Initialize DC_DATETIME type variable
DCDiffTimeCreate	Initialize DC_DIFFTIME type variable
assignment(=)	Initialize DC_DATETIME/DC_DIFFTIME variables
Eval	Get individual date/time components
toChar	Convert date/time to character string
EvalDay	Get as number of days (real type)
EvalHour	Get as number of hours (real type)
EvalMin	Get as number of minutes (real type)
EvalSec	Get as number of seconds (real type)
EvalNondim	Get as nondimensional time (real type)
EvalByUnit	Get in specified unit (day/hour/min/sec)
operator(+)	Addition (DC_DATETIME and DC_DIFFTIME types)
operator(-)	Subtraction (DC_DATETIME and DC_DIFFTIME types)
operator(*)	Multiplication (DC_DIFFTIME and numeric types)
operator(/)	Division (DC_DIFFTIME and numeric types)
mod	Remainder (between DC_DIFFTIME types)
operator(==)	Comparison (between DC_DATETIME types)
operator(>)	Comparison (between DC_DATETIME types)
operator(>=)	Comparison (between DC_DATETIME types)
operator(<)	Comparison (between DC_DATETIME types)
operator(<=)	Comparison (between DC_DATETIME types)
max	Return larger value
min	Return smaller value
SetZone	Change timezone
DCDateTimePutLine	Print DC_DATETIME variable information
DCDiffTimePutLine	Print DC_DIFFTIME variable information

The following procedures modify internal variables in dc_date_types:

Procedure	Description
SetCaltype	Change default calendar type
SetSecOfDay	Change default seconds per day

Other procedures:

Procedure	Description
ValidCaltype	Check if calendar type is valid
ValidZone	Check if timezone is valid
ZoneToDiff	Convert timezone to DC_DIFFTIME variable
ParseTimeUnits	Parse time unit and return unit symbol

Usage

Display Current Time

When DCDateTimeCreate subroutine is used on a DC_DATETIME type variable, the time is set. If year/month/day are not specified, current time is set. The set time can be converted to character type with toChar. See dc_string::Printf for Printf subroutine details.

program dc_date_sample1
  use dc_string, only: printf
  use dc_date, only: dc_datetime, dcdatetimecreate, tochar
  implicit none
  type(DC_DATETIME) :: time
 
  call dcdatetimecreate( time = time ) ! (out)
  call printf( fmt = 'current date and time is %c', c1 = trim( tochar(time) ) )
end program dc_date_sample1

Adding Date/Time Information

DC_DIFFTIME type variables express time differences. In the example below, variable diff is prepared and set to 25 days + 12 hours + 50 minutes using Create subroutine. By adding DC_DATETIME variable time_before and diff with operator(+), we get time_after which is 25 days + 12 hours + 50 minutes ahead of time_before.

program dc_date_sample2
  use dc_types, only: dp
  use dc_string, only: printf
  use dc_date, only: dc_datetime, dc_difftime, &
    & dcdatetimecreate, dcdifftimecreate, tochar, operator(+)
  implicit none
  type(DC_DATETIME) :: time_before, time_after
  type(DC_DIFFTIME) :: diff
 
  call dcdatetimecreate( time = time_before, & ! (out)
    & year = 2006, mon = 6,  day = 10, &       ! (in)
    & hour = 14,   min = 15, sec = 0.0_dp )    ! (in)
  call dcdifftimecreate( diff = diff, &        ! (out)
    & day = 25, hour = 12, min = 50)           ! (in)
 
  time_after = time_before + diff
 
  call printf( fmt = '%c + %c = %c', &
    & c1 = trim( tochar(time_before) ), c2 = trim( tochar(diff) ), &
    & c3 = trim( tochar(time_after) ) )
end program dc_date_sample2

Application to Time Integration Loop

Below is an example program solving dA/dt = -αA (initial value 1, α=0.0001) up to t = 12 (hours) using forward difference. By using DC_DIFFTIME for Δt, data output interval, and calculation time, loop termination and time comparison for data output become easy.

program dc_date_sample3
  use dc_types, only: dp
  use dc_date, only: dc_difftime, &
    & dcdifftimecreate, evalsec, evalbyunit, mod, &
    & operator(*), operator(==), operator(>)
  implicit none
  real(DP)                :: func_a = 1.0d0    ! Initial value of function A
  real(DP), parameter     :: alph   = 0.0001d0 ! Coefficient α
  character(*), parameter :: out_unit = 'hour' ! Unit for output time
  type(DC_DIFFTIME):: DelTimef, intervalf, calctimef
  integer :: i
continue
  call dcdifftimecreate( &            !       Δt = 5.0 (sec)
    & diff = deltimef, &              ! (out)
    & value = 5.0_dp, unit = 'sec')   ! (in)
  call dcdifftimecreate( &            !       Data output interval = 1.0 (min)
    & diff = intervalf, &             ! (out)
    & value = 1.0_dp, unit = 'min')   ! (in)
  call dcdifftimecreate( &            !       Calculation time = 12.0 (hour)
    & diff = calctimef, &             ! (out)
    & value = 12.0_dp, unit = 'hour') ! (in)
 
  open( 10, file='dc_date_sample.dat' )
  write(10,'(A,A,A)') '#  ', out_unit, '                value'
 
  i = 1
  do
    if (deltimef * i > calctimef) exit    ! Exit when past calculation time
 
    ! A_(n+1) = (1 - αΔt) * A_(n)
    func_a = (1.0 - alph * evalsec(deltimef)) * func_a
 
    ! Output data every intervalf (1 min)
    if (mod(deltimef * i, intervalf) == 0) then
      write(10,*) ' ', evalbyunit( deltimef * i, out_unit ), func_a
    end if
    i = i + 1
  end do
end program dc_date_sample3