System.Time.Clock Design Issues

David Menendez zednenem at
Mon Feb 7 23:44:32 EST 2005

Ketil Malde writes:

> Seth Kurtzberg <seth at> writes:
> > When you say [TAI is] "defined for all history and the future", does
> > that mean literally what it says? 
> Well, as it is only a clock (counting SI seconds), it is unambigously
> defined.  It is not a calendar, so you need a separate calendar to
> name days and years for you, and to perform the mapping between TAI's
> seconds and calendar entities.

As I understand it, TAI and UTC can both be described in terms of a
clock counting SI seconds. The difference is that a TAI day is always
86400 seconds long, whereas a UTC day can be 86399 - 86401 seconds,
depending on which second it is.

Using TAI, we can always convert a date and clock time to a count of
seconds and vice-versa without any additional information. To do the
same with UTC, we need a table of leap-seconds.
David Menendez <zednenem at> <>

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