[LEAPSECS] ] Fractional US civil time period representation is brittle

[Gerard Ashton]

Consider US eastern daylight time, June 30, 2012.

1/2 hour for the first hour of the day is 1800.0 SI seconds.
1/2 hour for the 19th hour of the day is 1800.5 SI seconds.

1/2 minute for the 1st minute of the day is 30.0 seconds.
1/2 minute for the 1139th minute of the day is 30.5 seconds.

This will make certain time computations quite intricate.
Representing the time as a simple floating point number may
lead to unexpected results.

Gerard Ashton