Is there any minhag (custom) when a person makes a siyum (finishes a mesacta or anything else that a "siyum" can be made on) that he himself doesn't say tachnun on that day?
What about in any of these situations:
He makes a siyum by night, would he not say the whole next day by shachris and mincha?
He makes a siyum after shachris but before mincha, would tachnun not be said by shachris (since this is the "day" of the siyum.) or only not by mincha.
Or perhaps any other situation.