Day and Date Functions

Liberty Basic Day and Date Routines

LB day-of-week conversion

This routine uses LB's built-in date$() function. In the LB universe, day 0 was Jan 1, 1901 and dates before 1/1/1901 return negative numbers.

It will accept 1- or 2-digit numbers for the month and day and 1, 2, 3 or 4-digit numbers for the year. Years from 0 to 99 are assumed as 2000 to 2099. It will also accept fully typed month names or 3-letter abbreviations.
Some examples: Jul 4, 06 -- July 04, 2006 -- 7/4/6 -- 07/04/2006

Be aware that negative years are incorrectly handled as positive, so LB's date$() function can not be relied upon for any date earlier than Jan 1, 100.

• -- - harmonv

' Return day-of-week for d$
function dayofweek$(dt$)
  day = date$(dt$) mod 7 + 7  ' +7 for dates before Jan 1, 1901
  select case (day mod 7)
    case 0: d$ = "Tuesday"
    case 1: d$ = "Wednesday"
    case 2: d$ = "Thursday"
    case 3: d$ = "Friday"
    case 4: d$ = "Saturday"
    case 5: d$ = "Sunday"
    case 6: d$ = "Monday"
  end select
  dayofweek$ = d$
end function

Gregorian Year, Month, Day to Julian Day #

' Convert Gregorian year,month,day to Julian Day #
function G2Jd(yr,mo,dy)
  a = int((14-mo)/12)
  y = yr + 4800 - a
  m = mo + 12*a - 3
  G2Jd = dy + int((153*m+2)/5)+365*y+int(y/4)-int(y/100)+int(y/400)-32045
end function

Julian Day to Gregorian Year, Month, Day

' Julian day to Gregorian date
function Jd2G(jd, byref yr, byref mo, byref dy)
  a = jd + 32044
  b = int((4*a+3)/146097)
  c = a - int((146097*b)/4)
  d = int((4*c+3)/1461)
  e = c - int(1461*d/4)
  m = int((5*e+2)/153)
  dy = e - int((153*m+2)/5) + 1
  mo = m + 3 - 12*int(m/10)
  yr = 100*b + d - 4800 + int(m/10)
end function

Gregorian Year, Month, Day to day-of-week

' Gregorian date to day-of-week (0=Sun, 1=Mon, ...)
function G2dow(yr,mo,dy)
  a = int((14-mo)/12)
  m = mo + 12*a - 2
  y = yr - a
  G2dow = (dy + y + int(y/4)-int(y/100)+int(y/400)+int(31*m/12)) mod 7
end function

The calculations for the Gregorian date and day routines are from Claus Tøndering's excellent Calendar FAQ page at http://www.tondering.dk/claus/calendar.html
They can be freely distributed for all non-commerical uses.

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