DESCRIPTION
ttag takes one argument on the command line
with can be either an event list time tag as a single floating point
value or a date/time specification in the form yy-mm-ddThh:mm:ss
and converts it into the respective other form:
ttag <tag> -> yy-mm-ddThh:mm:ss
ttag <timestamp> -> tag
The result is printed on standard output - return value is 0 upon
successful exit, otherwise.
otherwise.