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7-Feb-19 21:10

I know, it is the lounge... but I am not asking a programming question. It is more a philosophical one.

FILETIME = Contains a 64-bit value representing the number of 100-nanosecond intervals since January 1, 1601 (UTC).

time_t / Unix Timestamp = the number of seconds from Jan 1, 1970 (UTC)

I have found a lot of places using the same transformation rule where the offset is done by 116444736000000000LL which is exactly 369 years * 365 days * 24 hours * 3600 seconds * 10000000 (in 100 ns blocks)

But... what happens with leap years?

Thoughts?

(And before someone comes with the unnecessary commentary... yes, I am going to test it. This is just for the fun of a debate)

EDIT: My own shame, but to be fear I have to point to CPallinis answer below and copy my disclaimer / superlative facepalm here to avoid time waste for future readers...

Quote:

I did the calculations with the windows calculator ...

in programmer mode. Which means no decimals
116444736000000000 / 1000 / 3600 / 24 / 365 = 369
and not 369,24383561643835616438356164383562 (the right answer)

I need

M.D.V.

If something has a solution... Why do we have to worry about?. If it has no solution... For what reason do we have to worry about?
Help me to understand what I'm saying, and I'll explain it better to you
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modified 8-Feb-19 4:21am.

OriginalGriff7-Feb-19 21:22

OriginalGriff

7-Feb-19 21:22

Nelek wrote:
what happens with leap years?

"Then a miracle occurs"

Sent from my Amstrad PC 1640
Never throw anything away, Griff
Bad command or file name. Bad, bad command! Sit! Stay! Staaaay...
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Jörgen Andersson7-Feb-19 21:58

Jörgen Andersson

7-Feb-19 21:58

My daughter is born on the 29th of February. Smile | :)

Wrong is evil and must be defeated. - Jeff Ello

RugbyLeague8-Feb-19 0:31

RugbyLeague

8-Feb-19 0:31

She is born every 4 years?

CPallini7-Feb-19 21:26

7-Feb-19 21:26

Quote:
But... what happens with leap years?

Thoughts?

Such formula is wrong. Leap years did happen, after all. I am going to test it, of course, because I don't trust your own tests. Big Grin | :-D

Nelek7-Feb-19 22:07

7-Feb-19 22:07

CPallini wrote:
I am going to test it, of course, because I don't trust your own tests.

Neither do I... all is only a product of my imagination... or not? Laugh | :laugh:

M.D.V.

CPallini7-Feb-19 21:55

7-Feb-19 21:55

Made the test (and some computation).
The number 116444736000000000 is right, The formula is wrong,

369 years * 365 days * 24 hours * 3600 seconds * 10000000 = 116367840000000000

The difference is 89 days (one leap year every 4 years, with the exclusion of 1700, 1800, 1900).

Nelek7-Feb-19 22:15

7-Feb-19 22:15

I did the calculations with the windows calculator ...

in programmer mode. Which means no decimals
116444736000000000 / 1000 / 3600 / 24 / 365 = 369
and not 369,24383561643835616438356164383562 (the right answer)

D'Oh! | :doh:

I need

M.D.V.

Do not escape reality : improve reality !

Rage8-Feb-19 1:15

Rage

8-Feb-19 1:15

Nelek wrote:
n programmer mode

This is the most useless feature of the calculator. And the reason why I replaced the system calculator by the WinXP one.

Nelek8-Feb-19 1:18

8-Feb-19 1:18

sometimes it gets handy when masking or analyzing parts with big hexadecimal variables. The biggest problem is when you forget to change it back (as I just proved beyond doubt)

M.D.V.

CPallini8-Feb-19 2:31

8-Feb-19 2:31

Microsoft Calculator Plus - V.1.0 - 2004.
Possibly they still had some C/C++ developers at the time. Big Grin | :-D

Nelek8-Feb-19 5:03

8-Feb-19 5:03

I wanted to download from the official MS site... First you have to log in with a MS account, then it was still a problem and couldn't download it, because no device was associated with the account. D'Oh! | :doh:

They are doing such a good job... Dead | X|

I'll get from another place. Anyways... thank you

M.D.V.

CPallini8-Feb-19 9:48

8-Feb-19 9:48

If I remember well, I didn't download it from Mummy MS. Still it works like a charm.

Jörgen Andersson7-Feb-19 21:56

Jörgen Andersson

7-Feb-19 21:56

Julian or Gregorian time?

Wrong is evil and must be defeated. - Jeff Ello

OriginalGriff7-Feb-19 22:05

OriginalGriff

7-Feb-19 22:05

Gregorian: the first day of the Gregorian calendar was Friday, 15 October 1582 which is before the "start date" of the format.

Sent from my Amstrad PC 1640
Never throw anything away, Griff
Bad command or file name. Bad, bad command! Sit! Stay! Staaaay...
AntiTwitter: @DalekDave is now a follower!

CodeWraith7-Feb-19 22:51

CodeWraith

7-Feb-19 22:51

Simply forget about days, hours and minutes and take the exact length of a year and use that as a basis of your calculation. If you can keep the error small and do the conversion to your time units last, you should get a more accurate result. If you can keep the error small...

I have lived with several Zen masters - all of them were cats.

His last invention was an evil Lasagna. It didn't kill anyone, and it actually tasted pretty good.

jsc427-Feb-19 23:03

jsc42

7-Feb-19 23:03

Just treat a year as 365.2425 days (365 + 97/400), which is the basis of the Gregorian calendar : accurate to within 1 day in 30000 years. Except that the Earth's day and year are not constant (hence the need of occasional leap seconds [which is why Unix seconds are in the range 0 to 60, not 0 to 59]).

P.S. The Gregorian calendar was under the auspices of Pope Gregory (which one? too lazy to look up!) but actually was the work of a chap called Clavius, who got virtually no recognition for his work. Belatedly, that has been rectified - the largest crater on the far side of the Moon is named after him.

CodeWraith7-Feb-19 23:14

CodeWraith

7-Feb-19 23:14

jsc42 wrote:
Clavius

Yes, and in 2001 the guys at our moon base discovered a magnetic annomaly in that crater, which turned out to be an alien monolith device. It was placed there to notify its builders about us reaching the moon and discovering it.

Edit: I was mistaken. The moon base was at Clavius, the monolith was in the crater Tycho.

I have lived with several Zen masters - all of them were cats.

His last invention was an evil Lasagna. It didn't kill anyone, and it actually tasted pretty good.

modified 8-Feb-19 5:21am.

musefan8-Feb-19 2:59

musefan

8-Feb-19 2:59

I don't know if somebody covered this already, but you are doing a conversation and not a comparison. And because you are doing whole years (not partials) then leap years won't effect the result.

~~All you have to do is add/subtract 369 years. The number of days that passed by in those 369 years is irrelevant.~~

EDIT: In fact, you don't even do that. Just take the individual components (year, month, day, etc.) of one data type, and then apply those values to the other data type.