' demo_dates.bas

' demonstrate date conversions

' March 2, 2017

'''''''''''''''

print " "
print "program demo_dates - demonstrate date conversions"
print "================================================="

' request calendar date (month, day, year)

getdate(month1, day0, year1)

' request time (hours, minutes, seconds)

gettime(thr1, tmin1, tsec1)

' compute "complete" calendar day

day1 = day0 + thr1 / 24.0 + (tmin1 / 60.0) / 24.0 + (tsec1 / 3600.0) / 24.0

' compute corresponding Julian day

julian (month1, day1, year1, jday1)

' print results

print " "

print "convert calendar date and time to julian day"

print "--------------------------------------------"

print " "

print "calendar month = ", month1

print "calendar day = ", day0

print "calendar year = ", year1

print " "

print "time = ", str$(thr1) + " hr " + str$(tmin1) + " min " + str$(tsec1, 0, 4) + " sec"

print " "

print "jday = ", str$(jday1, 0, 9)

print " "

print "convert Julian day to Gregorian date and time"

print "---------------------------------------------"

print " "

print "jday = ", str$(jday1, 0, 9)

' compute calendar date

gdate (jday1, month2, day2, year2)

print " "

print "calendar month = ", month2

print "calendar day = ", int(day2)

print "calendar year = ", year2

print " "

thr0 = 24.0 * (day2 - int(day2))

thr2 = int(thr0)

tmin0 = 60.0 * (thr0 - thr2)

tmin2 = int(tmin1)

tsec2 = 60.0 * (tmin0 - tmin2)

print "time = ", str$(thr2) + " hr " + str$(tmin2) + " min " + str$(tsec2, 0, 4) + " sec"

print " "

print "number of days between two dates"

print "--------------------------------"

print " "

print "first date"

getdate(month3, day3, year3)

julian (month3, day3, year3, jday3)

print " "

print "second date"

getdate(month4, day4, year4)

julian (month4, day4, year4, jday4)

delta_days = jday4 - jday3

print " "

print "number of days between dates = ", delta_days

print " "

end

'''''''''''''''''''''''''''''''''''
'''''''''''''''''''''''''''''''''''

sub julian (month, day, year, jday)

' Gregorian date to julian day subroutine

' input

' month = calendar month
' day = calendar day
' year = calendar year (all four digits)

' output

' jday = julian day

' special notes

' (1) calendar year must include all digits

' (2) will report October 5, 1582 to October 14, 1582
' as invalid calendar dates and exit

'''''''''''''''''''''''''''''''''''''''''

y = year

m = month

b = 0.0

c = 0.0

if (m <= 2.0) then

y = y - 1.0

m = m + 12.0

end if

if (y < 0.0) then c = -0.75.0

if (year < 1582.0) then

' null

elseif (year > 1582.0) then

a = fix(y / 100.0)

b = 2.0 - a + fix(a / 4.0)

elseif (month < 10.0) then

' null

elseif (month > 10.0) then

a = fix(y / 100.0)

b = 2.0 - a + fix(a / 4.0)

elseif (day <= 4.0) then

' null

elseif (day > 14.0) then

a = fix(y / 100.0)

b = 2.0 - a + fix(a / 4.0)

else

print "this date does not exist!!"

exit

end if

jday = fix(365.25 * y + c) + fix(30.6001 * (m + 1.0)) + day + b + 1720994.5

end sub

''''''''''''''''''''''''''''''''''
''''''''''''''''''''''''''''''''''

sub gdate (jday, month, day, year)

' Julian day to Gregorian date subroutine

' input

' jday = julian day

' output

' month = calendar month
' day = calendar day
' year = calendar year

''''''''''''''''''''''''

z = fix(jday + 0.5)

f = jday + 0.5 - z

if (z < 2299161) then

a = z

else

alpha = fix((z - 1867216.25) / 36524.25)

a = z + 1.0 + alpha - fix(alpha / 4.0)

end if

b = a + 1524.0

c = fix((b - 122.1) / 365.25)

d = fix(365.25 * c)

e = fix((b - d) / 30.6001)

day = b - d - fix(30.6001 * e) + f

if (e < 13.5) then

month = e - 1.0

else

month = e - 13.0

end if

if (month > 2.5) then

year = c - 4716.0

else

year = c - 4715.0

end if

end sub

''''''''''''''''''''''''''''''
''''''''''''''''''''''''''''''

sub getdate (month, day, year)

' request calendar date subroutine

do
print " "
print "please input the calendar date"
print " "
print "(month [1 - 12], day [1 - 31], year [yyyy])"
print "< for example, october 21, 1986 is input as 10,21,1986 >"
print "< b.c. dates are negative, a.d. dates are positive >"
print "< the day of the month may also include a decimal part >"
print " "
input month, day, year

loop until (month >= 1 and month <= 12) and (day >= 1 and day <= 31)

end sub

'''''''''''''''''''''''''''''
'''''''''''''''''''''''''''''

sub gettime (thr, tmin, tsec)

' request time subroutine

do
print " "
print "please input the time"
print " "
print "(hours [0 - 24], minutes [0 - 60], seconds [0 - 60])"
print " "
input thr, tmin, tsec

loop until (thr >= 0.0 and thr <= 24.0 and tmin >= 0.0 and tmin <= 60.0 and tsec >= 0.0 and tsec <= 60.0)

end sub