However, certain binary representations of Unix times are particularly significant.

A Unix time number can be represented in any form capable of representing numbers.

The Unix time number increases by exactly 86400 each day, regardless of how long the day is.

Two layers of encoding make up Unix time.

As the use of Unix time has spread, so has the practice of celebrating its milestones.

The database attempts to record historical time zones and all civil changes since 1970, the Unix time epoch.

Unix time may be checked on some Unix systems by typing on the command line.

This TAI-based system, despite its superficial resemblance, is not Unix time.

Unix enthusiasts have a history of holding parties to celebrate significant values of the Unix time number.

A full list of these data structures is virtually impossible to derive but there are well-known data structures that have the Unix time problem.

If given a Unix time number that is ambiguous due to a positive leap second, this algorithm interprets it as the time just after midnight.

Unix has no tradition of directly representing non-integer Unix time numbers as binary fractions.

Many computer systems internally store points in time in Unix time format or some other System time format.

The above scheme means that on a normal UTC day, of duration 86400 seconds, the Unix time number changes in a continuous manner across midnight.

The basis of such Unix times is best understood to be an unspecified approximation of GMT.

As indicated by the definition quoted above, the Unix time scale was originally intended to be a simple linear representation of time elapsed since an epoch.

When a leap second occurs, so that the UTC day is not exactly 86400 seconds long, a discontinuity occurs in the Unix time number.

Observe that when a positive leap second occurs (i.e., when a leap second is inserted) the Unix time numbers repeat themselves.

Several later problems, including the complexity of the present definition, result from Unix time having been defined gradually by usage rather than fully defined from the outset.

In this type of system the Unix time number violates POSIX around both types of leap second.

Commonly a Mills-style Unix clock is implemented with leap second handling not synchronous with the change of the Unix time number.

Since times before 1970 are rarely represented in Unix time, one possible solution that is compatible with existing binary formats would be to redefine as "unsigned 32-bit integer".

When a leap second is deleted, the Unix time number jumps up by 1 where the leap second was deleted, which is the end of the day.

If given a Unix time number that is invalid due to a negative leap second, it generates an equally invalid UTC time.

(A standard Unix time system must similarly consult a leap second table to convert to and from TAI, but this is a much rarer requirement.)