dcdatetimemod.f90

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! -*- mode: f90; coding: utf-8 -*-
!-----------------------------------------------------------------------
! Copyright (c) 2000-2026 Gtool Development Group. All rights reserved.
!-----------------------------------------------------------------------
 
function dcdatetime_mod_ff(diff1, diff2) result(result)
 
  use dc_date_internal, only: dcdate_normalize, dcdate_nondimcheck
  use dc_date_types, only: cyclic_mdays, dc_datetime, dc_difftime
  use dc_scaledsec, only: dc_scaled_sec, &
    & operator(==), operator(<), operator(>), operator(<=), operator(>=), &
    & operator(+), operator(-), operator(*), operator(/), &
    & modscl => mod, modulo, int, abs, sign
  implicit none
  type(dc_difftime):: result
  type(dc_difftime), intent(in):: diff1, diff2
  type(dc_scaled_sec):: sec1, sec2
  type(dc_scaled_sec):: zero_sec
continue
  result % day_seconds = diff1 % day_seconds
  if (diff1 % day == zero_sec .and. diff2 % day == zero_sec .and. &
    & diff1 % sec == zero_sec .and. diff2 % sec == zero_sec) then
    result % mon = modscl(diff1 % mon, diff2 % mon)
    result % day = zero_sec
    result % sec = zero_sec
  else if (diff1 % sec == zero_sec .and. diff2 % sec == zero_sec) then
    result % mon = zero_sec
    result % day = modscl((cyclic_mdays * diff1 % mon + diff1 % day), &
      & (cyclic_mdays * diff2 % mon + diff2 % day))
    result % sec = zero_sec
  else
    sec1 = diff1 % day_seconds * (cyclic_mdays * diff1 % mon + diff1 % day) &
      & + diff1 % sec
    sec2 = diff2 % day_seconds * (cyclic_mdays * diff2 % mon + diff2 % day) &
      & + diff2 % sec
    result % sec = modscl(sec1, sec2)
    result % day = zero_sec
    result % mon = zero_sec
    call dcdate_normalize(result % day, result % sec, result % day_seconds, result % nondim_flag)
  endif
  call dcdate_nondimcheck('dc_date#mod', diff1, diff2, result)
end function dcdatetime_mod_ff