Get the scheduled start time of a task or nil
if the task is not scheduled.
This function does not generate a change.
task.at()
None
Returns the scheduled start time of a task or nil
if the task is not scheduled.
Example usage task.at():
t = task(datetime('2022-01-01'), ||log('Dummy task'));
t.at();
Return value in JSON format
"2022-01-01T00:00:00Z"