15.5.3 File Time

As stated above, file time is operating-system dependent. As of this writing, two formats are used. For unix and Windows systems, file time is the number of seconds since midnight January 1, 1970 UTC (the standard unix time convention).

OS/2 represents file time as a 32-bit unsigned integer, in which the time components are broken down into unsigned bit fields. The components are always stated in local time. The fields, from MSB to LSB, are:

• 7 bits representing the year, relative to 1900.
• 4 bits representing the month, numbered 1 to 12.
• 5 bits representing the day of the month, numbered 1 to 31.
• 5 bits representing the hour of the day, numbered 0 to 23.
• 6 bits representing the minute, numbered 0 to 59.
• 5 bits representing the second. This field is unusual in that it counts units of two seconds, so it is a number between 0 and 29, representing second counts corresponding to 0 through 58.

The following procedures generate their results in file-time format:

     file-access-time
     file-access-time-direct
     file-access-time-indirect
     file-modification-time
     file-modification-time-direct
     file-modification-time-indirect
     file-attributes/access-time
     file-attributes/modification-time
     file-attributes/change-time

Additionally, set-file-times! accepts its time arguments in file-time format.