Comparing time value formats
From EtherWiki
Datetime object
The add_duration() method takes a parameter that represents a duration in a single unit of time as DURATION[y|M|d|h|m|s].
The format() method takes a parameter that uses the Java date format pattern syntax.
The format_difference() method formats the datetime value as HH:mm:ss.
The sensor service minimum_update property takes an integer value in milliseconds.
The timer service duration property takes a value formatted as h:m:s, m:s, or s.
