DT_DateToSec

[Michael Clease]

I was looking at DT_DateToSec and was wondering where it does its calculation from is it 01-01-1970 or 01-01-1900 or ??

[ErosOlmi]

As far as I know it starts from date "01-01-0000" so from the first day of the first month of year zero.
Roberto will be more precise.

Number of seconds of the very first day:

uses "Console", "dt"
printl DT_DateToSec("01-01-0000")
waitkey

[peralta_mike]

Subj: DT_DateToSec and DT_SecTo_Date Only Seem To Work for > 4 A.D. or so.

If you try the following tb script the functions
DT_DateToSec and DT_SecTo_Date
only seem to work for > 4 A.D. or so.

'=====================================================
uses "console","dt"
 
console_write "01-01-1970 -> " & dt_datetosec("01-01-1970") & $CRLF
console_write "01-01-0004 -> " & dt_datetosec("01-01-0004") & $CRLF
console_write "01-01-0001 -> " & dt_datetosec("01-01-0001") & $CRLF
console_write "01-01-0000 -> " & dt_datetosec("01-01-0000") & $CRLF
console_write "63000000000 secs -> " & dt_sectodate(63000000000) & $CRLF
console_write "10000000000 secs -> " & dt_sectodate(10000000000) & $CRLF
console_write "1000000000 secs -> "  & dt_sectodate(1000000000) & $CRLF
console_write "100000000 secs -> "   & dt_sectodate(100000000) & $CRLF
console_write "10000000 secs -> "    & dt_sectodate(10000000) & $CRLF
console_write "1000000 secs -> "     & dt_sectodate(1000000) & $CRLF
console_write "100000 secs -> "      & dt_sectodate(100000) & $CRLF
console_write "10000 secs -> "       & dt_sectodate(10000) & $CRLF
console_write "1000 secs -> "        & dt_sectodate(1000) & $CRLF
console_write "100 secs -> "         & dt_sectodate(100) & $CRLF
console_write "10 secs -> "          & dt_sectodate(10) & $CRLF
console_write "1 secs -> "           & dt_sectodate(1) & $CRLF
console_write "0 secs -> "           & dt_sectodate(0) & $CRLF
console_waitkey
'===================================================

[peralta_mike]

Can this be fixed?
Also how can I confirm that the datetosec and sectodate formulas are working correctly for dates after Jan 1, 1970 ?

[peralta_mike]

Any info on this?

[ErosOlmi]

I will check this night when back home

[Simone]

Hi all,

I know why the function "DateToSec" doesn't work, for now the first date that work is 01-01-0002

I talk about this problem with Eros.

Ciao,
Simone

[zak]

there is a book of Peter Duffett-Smith : Practical Astronomy With Your Calculator

describe how to find the number of days lapsed from year January 1, 4713 BC Greenwich noon http://en.wikipedia.org/wiki/Julian_day to any day of choice. so the julian day begins at 12 noon. if i am not wrong we can convert it to seconds by *24*60*60. the algorithm described in page 7 . may be this info can be used somehow. attached page 7 from google books i salvages from temporary internet files cache, i hope it is not harming the book copyright, if so Eros can delete it. i have tried the algorithm in the book to see the days between 1902,1,17 and 2011,4,26, it turns that it is 39911 days and using the DT_DateToSec it return 39911.
i think the zero year in astronomy is like 1900, 1800, etc
this site also calculate julian days
http://aa.usno.navy.mil/data/docs/JulianDate.php
http://www.hermetic.ch/cal_stud/jdn.htm

Uses "Console", "dt" 
Dim dt,dt2,difdt As Extended
dt = DT_DateToSec("01-17-1902")
dt2 = DT_DateToSec("04-26-2011")
difdt=(((dt2-dt)/60)/60)/24  'number of days between ...
PrintL difdt 
Dim days, daysTo, dif  As Extended
days = julian(1902,1,17)
days = days - 0.5
daysTo = julian(2011,4,26) 
daysTo = daysTo - 0.5
dif = daysTo - days
PrintL dif
WaitKey
'=========================================== 
Function julian(y As Extended,m As Extended,d As Extended)
Dim y1,m1,d1,B,C,DD,A,JD As Extended
If m=1 Or m=2 Then
  y1=y-1:m1=m+12
  Else 
  y1=y:m1=m
End If
If y>=1582 Then
  A=Int(y1/100)
  B=2-A+Int(A/4)
  Else
     B=0
End If
If y1<0 Then
  C=Int(365.25*y1)-0.75
  Else
    C=Int(365.25*y1)
End If
DD=Int(30.6001*(m1+1))
JD=B+C+DD+d+1720994.5
Function = JD
End Function

[ErosOlmi]

Ok, I think I've got something working hopefully.

Please get attached thinBasic Date module and manually copy into thinBasic library directory in this way: unzip "thinBasic_DT.DLL" into \thinBasic\Lib\ directory replacing your current file.

I've made some tests but not all the tests I would have liked. Tomorrow, with the help of Simone, I will perform more tests and if needed I will amend again Date module. For your info, I work together with Simone in an Italian company.

The following code seems working as expected. If you have some tests resulting in wrong output, just post your code and I will have a look tomorrow.

Uses "Console"
Uses "DT"

DT_SetDateSeparator("/")

Dim lCounter As Long
Dim nDates As Long = 12
Dim sDates(nDates) As String

sDates( 1) = DT_GetDate
sdates( 2) = "01-01-1970"
sdates( 3) = "01-17-1902"
sDates( 4) = "02-29-0004"
sDates( 5) = "01-01-0003"
sDates( 6) = "12-31-0002"
sDates( 7) = "01-01-0001"
sDates( 8) = "12-31-0000"
sDates( 9) = "12-30-0000"
sDates(10) = "01-02-0000"
sDates(11) = "01-01-0000"
sDates(12) = "00-00-0000"

For lCounter = 1 To nDates
  If Len(sDates(lCounter)) = 0 Then Iterate For
  PrintL  "DateToSec: " & sDates(lCounter) & " -> " & RSet$(DT_DateToSec(sDates(lCounter)), 12) & "      " & _
          "SecToDate: " & DT_SecToDate(DT_DateToSec(sDates(lCounter)))
Next

PrintL "---Press any key to continue---"
WaitKey

Output of the above program:

DateToSec: 04/26/2011 ->  63471081600      SecToDate: 04/26/2011
DateToSec: 01-01-1970 ->  62167305600      SecToDate: 01/01/1970
DateToSec: 01-17-1902 ->  60022771200      SecToDate: 01/17/1902
DateToSec: 02-29-0004 ->    131414400      SecToDate: 02/29/0004
DateToSec: 01-01-0003 ->     94780800      SecToDate: 01/01/0003
DateToSec: 12-31-0002 ->     94694400      SecToDate: 12/31/0002
DateToSec: 01-01-0001 ->     31708800      SecToDate: 01/01/0001
DateToSec: 12-31-0000 ->     31622400      SecToDate: 12/31/0000
DateToSec: 12-30-0000 ->     31536000      SecToDate: 12/30/0000
DateToSec: 01-02-0000 ->       172800      SecToDate: 01/02/0000
DateToSec: 01-01-0000 ->        86400      SecToDate: 01/01/0000
DateToSec: 00-00-0000 ->            0      SecToDate: 00/00/0000
---Press any key to continue---

[peralta_mike]

My tests so far show good results.
Later, I will compare more recent dates against my Perl and C library results.

Thanks.

btw
There are only 4 digits in the year.
What about when we hit the year 10000?
The dreaded Y10K problem.
lol, hehehe just kidding.
We won't have to worry about that for a while.


' --- trydt.bas April 27, 2011 ---
uses "console","dt"
console_write "01-01-1970 -> " & dt_datetosec("01-01-1970") & $CRLF
console_write "01-01-0004 -> " & dt_datetosec("01-01-0004") & $CRLF
console_write "01-01-0003 -> " & dt_datetosec("01-01-0003") & $CRLF
console_write "01-01-0002 -> " & dt_datetosec("01-01-0002") & $CRLF
console_write "01-01-0001 -> " & dt_datetosec("01-01-0001") & $CRLF
console_write "01-01-0000 -> " & dt_datetosec("01-01-0000") & $CRLF
console_write "63000000000 secs -> " & dt_sectodate(63000000000) & $CRLF
console_write "10000000000 secs -> " & dt_sectodate(10000000000) & $CRLF
console_write "1000000000 secs -> " & dt_sectodate(1000000000) & $CRLF
console_write "100000000 secs -> " & dt_sectodate(100000000) & $CRLF
console_write "10000000 secs -> " & dt_sectodate(10000000) & $CRLF
console_write "1000000 secs -> " & dt_sectodate(1000000) & $CRLF
console_write "100000 secs -> " & dt_sectodate(100000) & $CRLF
console_write "10000 secs -> " & dt_sectodate(10000) & $CRLF
console_write "1000 secs -> " & dt_sectodate(1000) & $CRLF
console_write "100 secs -> " & dt_sectodate(100) & $CRLF
console_write "10 secs -> " & dt_sectodate(10) & $CRLF
console_write "1 secs -> " & dt_sectodate(1) & $CRLF
console_write "0 secs -> " & dt_sectodate(0) & $CRLF
console_waitkey