You can set the time frame for a Calendar-Based Task when you create or edit a task. See the types of time frames below.
When you set a specific time, you decide for the assignee of the task when to begin the task - at the "Start date" and "Start time" set by you.
Flexible Time Frame
When you set a flexible time frame, the assignee of the task decides for themselves when to begin and complete the task - anytime between the "Can start from" date and time and the "Must finish before" date and time set by you.
The timezone of the task is set according to the timezone of the listing.