A Time Pattern is a collection of multipliers that can be applied to a quantity to allow it to vary over time. Water demands, reservoir heads, pump schedules, and water quality source inputs can all have time patterns associated with them.
The time interval used in all patterns is set with the project's Time Options. Within this interval a quantity remains at a constant level, equal to the product of its nominal value and the pattern's multiplier for that interval. Although all time patterns must utilize the same time interval, each can have a different number of periods. When the simulation clock exceeds the number of periods in a pattern, the pattern wraps around to its first period again.
As an example of how time patterns work consider a junction node with an average demand of 10 GPM. Assume that the time pattern interval has been set to 4 hours and a pattern with the following multipliers has been specified for demand at this node:
| Period | 1 | 2 | 3 | 4 | 5 | 6 |
| Multiplier | 0.5 | 0.8 | 1.0 | 1.2 | 0.9 | 0.7 |
Then during the simulation the actual demand exerted at this node will be as follows:
| Hours | 0-4 | 4-8 | 8-12 | 12-16 | 16-20 | 20-24 | 24-28 |
| Demand | 5 | 8 | 10 | 12 | 9 | 7 | 5 |