Very often, we are asked how charter companies count the number of days for a typical 7-day charter. Quite frankly, a) it can be confusing; and b) it can make you can needlessly waste sailing time without realizing it when you book your charter.
Before anything else, understanding this: No matter how one slices it, what counts is which day and time the boat is made available to you, charter ready, and which day and time you have to leave the boat, emptied, cleaned and all. Contemplate the following.
Situation 1: Noon to noon charters
Most companies in the Caribbean use that configuration. Say you start on a Saturday: your boat is available for boarding Saturday at noon. You will have to leave the boat the following Saturday at noon. That is a true 7-day/7-night charter (the standard).
However, in reality, when you board the boat at noon, as you can imagine, you do not cast off at 5 minutes past noon. By the time you have received the boat briefing (which cannot take place until the boat is officially available to you) and processed the entire list of pre-castoff items, it usually is already past the time when you can safely leave for your first sailing leg. Especially in winter time, when sunset is early in the Caribbean. As a result, you will spend your first night at the dock and leave Sunday morning for a charter which, in reality, started on Saturday morning, and was paid for accordingly.
TIP: That is why many charterers, who want their full 7-day sailing vacation, take advantage of the 'sleep aboard' a.k.a. 'early start'', charged at 50% of the daily rate. See below why this is increasingly popular.
In the case above, the boat will be available Friday night at 5 or 6PM. You will sleep aboard - which, if your party has 3 or 4 couples, is much cheaper than paying for 3 or 4 hotel rooms. If you arrive at the base, say, Friday at the beginning of the afternoon, you have time to provision, store everything on the boat, settle everyone aboard, proceed with all your checklists, spend the night, attend the briefing at 9AM and get on your way on Saturday at 10:30AM at the latest.
That way, in fact, by paying for only an extra half day for the sleep aboard, you gain an entire sailing day.
Situation 2: 5 or 6PM boarding time to 11AM charter-ending time
Same case study as above: you book your charter from Saturday to Saturday. You show up on Saturday at the base. Your charter starts at 6PM and ends the following Saturday at 11AM. That is a 6 & 1/2-day / 7-night charter. In other words, you have to use part of your Sunday morning to provision, do the briefing, etc. Note: If this is the case with the charter company you are considering, make sure it is charging you for only 6 & 1/2 times the day rate, and not for 7.
With those charter companies, if you want your full 7-day sailing charter as in case #1, you must buy an extra full day to be allowed to board the boat on Friday at 6PM. Or sometimes, you may buy another 1/2 day to have the boat available on Saturday at noon.
Incidentally, if a company using the noon-to-noon configuration offers 9 days for 7, a Saturday to Saturday charter should end on the following Monday at noon. That is a genuine 9-day charter. So simply compare what the 7 "day" standard charter is, with the 9 "day" charter that is offered and see what kind of deal it really is.
Situation 3: The Med.
In the Med., for a mysterious reason, it may often get worse. Many companies use this: a 7-night charter starts on a Saturday at 6PM and ends the following Saturday at 8AM. Means that a 7-night charter is in fact a 6-day charter. Or worse, considering that, in order to give the boat back at 8AM, you must, in fact be back the night before.
In conclusion, when you compare rates between charter companies, make sure you line up exactly the same number of days for all companies, before comparing the final ands total rates.