My wife menstrual cycle is irregular.8 dec 2012, 10 jan 2013, 16 feb 2013, 20 march 2013.I want to find out the accurate & exact ovulation date/days?

12-14days pre menses. In general, ovulation occurs 12-14days prior to menses. Start checking ovulation kit about day 12 of menses and continue until positive, day 14-19 probably for her.