Month and year intervals

Recurring tasks can have a scheduling rule with repeat intervals of months or years.

Maintenix calculates the deadline for the next occurrence of a task with repeat interval of months (CMON) as follows:

  • If the previous task is completed on the last day of a month, the next due date is the specified interval of months later, on last day of the month. Given the uneven number of days in calendar months, the number of days that pass in the interval of months before the next task is due, varies.
  • If the previous task is completed on any other day of the month (except January 29 and 30), the next due date is the specified interval of months later, on the same day of the month.
  • If the previous task is completed on January 29 or on January 30 and the interval is one month, the next due date is February 28, or February 29 if it's a leap year. However, if the interval is more than one month, then the next occurrence is the specified interval of months later, on the same day of the month.

The following examples show previous task completion dates, monthly repeat intervals, and the resulting next due date for tasks.

Completion date of the previous task Repeat interval Next due date
September 30 6 months March 31
March 31 6 months Sept 30
November 30 3 months February 28
July 15 4 months November 15
January 29 1 month February 28
January 29 2 months March 29
January 30 1 month February 28
January 31 1 month February 29 (leap year)

For tasks that have a deadline repeat interval specified in calendar years (CYR), Maintenix considers the months with different number of days, and the leap years. The following table provides examples of how Maintenix schedules such tasks.

Completion date of the previous task Repeat interval Next due date
February 28, 2015 1 year February 29, 2016 (leap year)
February 29, 2016 1 year February 28, 2017
March 15, 2015 1 year March 15, 2016
January 1, 2016 10 years January 1, 2026