According to the Fertility Friend website we use to do our charts, it could be during any of those times. That's why they don't recommend relying on it solely. I notice that I tend to get a + on the ovulation tests and the following day I get ovulation pains.
Im the same as Bagpuss, I get them the day or so after I get positive OPK's so I presume its at the time of ovulation. I always seem to get the pains in the evening.