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.

Processed Files

Julian Dates start from Jan 1, 4713 BC

EventJulian DateTimedate
Epoch 12h UT Jan 0.5 19002,415,020.0208,657,728,000.0 secs
GPS time zero 0h Jan 6 19802,444,244.5211,182,724,800.0 secs
0h Jan 1, 19802,444,239.5211,182,292,800.0 secs
0h Jan 1, 20002,451,544.5211,813,444,800.0 secs

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