The time it takes for water to freeze in a typical freezer varies depending on a number of factors. The first factor to consider is the amount of water being frozen.
If two water glasses are placed in the freezer at the same time and one is filled only a third of the way, while the other is filled halfway, the one with less water freezes first. The size of the glass is a factor as well.
Another factor is the temperature that the water started at. If there are two glasses, and one is filled with cold water that has been chilled by an ice cube and the other glass is filled with hot water that has been boiled, and both are placed in the freezer at the same time, the water in the one that started out colder freezes faster.
The temperature of the freezer itself is yet another factor. If there are two glasses with the same amount of water in each and the liquid contained in them begins at the same temperature, then the external source of cold determines how long the freezing process takes. A very cold freezer causes the water to freeze faster than a freezer that is only moderately cold.