GeoNav and Y2K
GeoNav Date & Time
Functions
GeoNav obtains the current date
and time from the DOS operating system (DOS & Windows 95
& 98). It does not obtain date or time directly from the computer
BIOS. Dates accepted by DOS are generally restricted to the Year
range 1980 to 2099.
We have not experienced any problems with GeoNav
data acquisition and processing while simulating year 2000
roll-overs.
GeoNav RAW Files
GeoNav year text functions are always full value not
shortened to 2 characters (eg 2000 not 00).
GeoNav RAW data files
store dates as the number of days since January 1, 1980 and times as the number of seconds and fractions of seconds since mid-night.
The current GeoNav RAW file date format functions
correctly for all dates within the range January 1st 1900 to November
17th 2065.
Imported Files
In
cases where third party data files containing dates are imported to
GeoNav, as in the tide editing routines, 2 digit year
values are added to 2000 if they are between 0 and 50, and
added to 1900 if they are greater than 50.
Processed
Files
Dates in processed GeoNav data files are stored as
double precision Timedates in Julian seconds.
GeoNav
date and Julian Timedate routines function correctly for all dates from
January 1st 4713 BC. Years BC are negative, there is no year zero and
there are no dates from 5/10/1582 to 14/10/1582 inclusive, in accordance
with the Gregorian calendar.
Julian Dates
Julian Dates start from Jan 1, 4713 BC
| Event | Julian Date | Timedate |
| Epoch 12h UT Jan 0.5 1900 | 2,415,020.0 | 208,657,728,000.0 secs |
| GPS time zero 0h Jan 6 1980 | 2,444,244.5 | 211,182,724,800.0 secs |
| 0h Jan 1,
1980 | 2,444,239.5 | 211,182,292,800.0 secs |
| 0h Jan 1,
2000 | 2,451,544.5 | 211,813,444,800.0
secs |
If you require any further information regarding GeoNav, please ring, fax or email.
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