Does a divorce occur if a man swears by divorce not to do something, with the intention of not doing it for one day, then forgets this intention and does it months later?

The fatwa dictates that whoever swears an oath by divorce and then breaks it, their divorce occurs. The intent of the swearer is what matters in an oath. If he intended the action or the refraining from an action within a specific time, his oath is restricted to that time.

So, if you swore to refrain from something and intended to refrain from it on a specific day, you would break your oath by doing it on that day only, and no other.

If you are unsure about your intention, reference should be made to the reason for the oath. If the reason necessitates specifying a day, then it is specified to that day. Otherwise, it is by performing this action at any time.

If you break your oath, your divorce occurs and the oath is dissolved. It is permissible to take your wife back during her 'iddah (waiting period) if this divorce does not complete the three divorces.

It must be noted that the lawful oath is by Allah Almighty, whereas swearing by divorce is among the oaths of the dissolute.