Time Increment is an optional literal in certain math toolbox functions (Advanced functions, MAVG, WMAXn, etc..) that specifies the times (slots) the calculation should look for data in.  The available time increments are:

BYDAY

BYHOUR

BYQTRHOUR - For 15 minute frequency variables.

BYHALFHOUR - For 30 minute frequency variables

BYMINUTE

BY4HOUR

BY5MINUTE

Example: Calculate the Weekly Maximum of a four hour variable.

Since we are only calculating one value a week, we will setup our calculated var as a Daily Calculation. We MUST use the optional Time Increment parameter of the WMAXn math toolbox function. Since the source variable's frequency is 4 hour we need to set the Time Increment to BY4HOUR.

V17536 - A four hour parameter.
V17537 - A Daily Calculation with equation set to WMAX7(C17356,BY4HOUR). The formula will return the maximum value of variable 17356 for the week definition 7 (Sunday thru Saturday) and will look for data every 4 hours(BY4HOUR).

WARNING: The Time Increment should match the frequency of the source or input variable (V17536). If we do not specify the Time Increment the function will use a time increment of the target or calculated variable(V17537). Since that variable is daily, BYDAY would be used. This would return the wrong result. Since the formula Time Increment would be BYDAY, the formula would look at the first 4 hour period of Sunday, July 6th, increment by 1 day and look at the first 4 hour period of the 7th (and find .07, NOT .14), increment by 1 day, etc... Therefore, it would only look at the first value of each day to find the Max. It would therefore not find the 0.14 at 8:00AM.

See Also: Working with Daily Detail Variables in Calculations