There is no standard lab report format. Instructors may handle this issue any way they choose. Often it is left up to the TA's to require a specific format. If a student does a lab on Tuesday, the report would be due by a specified time Thursday evening. Forty eight hours gives the students sufficient time to do the write-up while it is still fresh in their mind.
Some instructors choose to have the lab report turned in at the end of the lab session.
If this is done, the lab hours are extended by one hour to give the students time to complete the write-up. At the beginning of the term, the slots are labeled with the course name, TA's name, and the TA's lab sections. The lab reports are turned in to these marked slots. Fractional parts of a point may be awarded. Some faculty do not accept late lab reports.