I just noticed that the definition of the constants have 0.5 in it. Why?
from dateh.inc
const
JulianEpoch = TDateTime(-2415018.5);
UnixEpoch = JulianEpoch + TDateTime(2440587.5);Dennis
Mailing lists / fpc-pascal / 2017-08
why the 0.5 in the Unix Epoch (for UnixToDateTime function)
6 messages · 5 people ·
- Vojtěch Čihák 2
- Dennis 1
- Dennis Poon 1
- Mark Morgan Lloyd 1
- Paul Nance 1
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Hi,
wiki https://en.wikipedia.org/wiki/Julian_day says that "... Julian day number 0 assigned to the day starting at noon on January 1, 4713 BC, ..." The noon means 0,5.
V.
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Show quoted text 5 lines
Od: Dennis
Komu: FPC-Pascal users discussions
Datum: 01.08.2017 13:14
Předmět: [fpc-pascal] why the 0.5 in the Unix Epoch (for UnixToDateTime function)
I just noticed that the definition of the constants have 0.5 in it. Why?
from dateh.inc
const
JulianEpoch = TDateTime(-2415018.5);
UnixEpoch = JulianEpoch + TDateTime(2440587.5);Dennis
Hi,
wiki https://en.wikipedia.org/wiki/Julian_day says that "... Julian day number 0 assigned to the day starting at noon on January 1, 4713 BC, ..." The noon means 0,5.
V.
______________________________________________________________
Show quoted text 5 lines
Od: Dennis
Komu: FPC-Pascal users discussions
Datum: 01.08.2017 13:14
Předmět: [fpc-pascal] why the 0.5 in the Unix Epoch (for UnixToDateTime function)
I just noticed that the definition of the constants have 0.5 in it. Why?
from dateh.inc
const
JulianEpoch = TDateTime(-2415018.5);
UnixEpoch = JulianEpoch + TDateTime(2440587.5);Dennis
Vojtěch Čihák wrote 9 lines
Hi,
wiki https://en.wikipedia.org/wiki/Julian_day says that "... Julian
day number 0 assigned to the day starting at noon on January 1, 4713
BC, ..."
The noon means 0,5.
Thanks,
that is a weird definition though IMHO.
Dennis
Dennis Poon wroteVojtěch Čihák wrote:>> Hi,>> wiki https://en.wikipedia.org/wiki/Julian_day says that "... Julian > day number 0 assigned to the day starting at noon on January 1, 4713 > BC, ...">> The noon means 0,5.>Thanks,that is a weird definition though IMHO.
Astronomer's convention.
Mark Morgan Lloyd
markMLl .AT. telemetry.co .DOT. uk
[Opinions above are the author's, not those of his employers or colleagues]
I just noticed that the definition of the constants have 0.5 in it. Why? from dateh.inc…
Actually the Julian calendar started at noon, the 0.5 is added to get to midnight. The Julian calendar was developed for astronomers, who view the sky when it gets dark and want all observing to be referenced to the same date. Us normal people start our day at midnight so we have to add the extra half day. -- Paul
"Dennis" wrote 15 lines
I just noticed that the definition of the constants have 0.5 in it.
Why?
from dateh.inc
const
JulianEpoch = TDateTime(-2415018.5);
UnixEpoch = JulianEpoch + TDateTime(2440587.5);
Dennis
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