What time does the match start? What does NOT BEFORE mean?
The times of matches should appear in your local timezone on the Schedule of Play – the ‘order of play’, so if you are in the UK you will see GMT or BST in the summer months.
The “Not before” is a rough estimate of the planned start time – this will be shown when there is a preceding match on the court and of course it could over-run and delay the subsequent match. Very few matches in tennis have a definitive start time – except for the first match of the day or the session – for this reason.