You can add a task with a specific time spent and on a specific date running the following command:

$ timetracking add <task> <time_spent> [date]
or
$ tm a <task> <time_spent> [date]

The <time_spent> parameter must be like this: 1h | 15m | H:mm | HH:mm.

By default [date] paremeter must be in the format MM/dd/yyyy and you can pass the start time as h:mm. If the [date] is not given the summary will be the current date/time. The date format can be configured by the configuration file, see Installation section.