Does anybody know the mourning time in England around the 12th century?

Mourning was not the elaborate ritual it became much later. For instance, people did not have special mourning clothes, it would have been far too expensive for most. most people were buried without tombstones, so there was no ritual of visiting the grave etc. prayers were said for the soul of the dead though, it was believed this would shorten a person's time in purgatory and help them get to heaven quicker. There was no stipulation about how soon after a spouse's death the survivor could remarry. obviously some felt more strongly about the death of a spouse which might affect the desire to remarry.

It could have depended on the status of the mourners. A poor man with children would need to find a wife quickly, to take care of them, a poor woman might find it more difficult, but she would need to find a husband if she could. Chaucer, writing in the 14th century describes the Wife of Bath following her husband's coffin to the grave but looking at his young apprentice, whom she hoped would replace him.