There are several types of time conditions that can be added - when you choose to add a time condition, the first thing you need to do is to select which time condition in the drop down list of available options - the list is shown here.
The condition can be set to a specific time (1:00pm, n minutes before sunrise, etc.) or to a range of time (between midnight and sunrise, day time, etc.).
When setting to a specific time, type that time in the Time/Offset
field at right, as shown in this example: 
When setting the Time Condition
field to an offset time (15 minutes before sunset, etc.), set the time
offset value in this field, as shown in this example: