From Wiktionary, the free dictionary
From тогда́ (togdá) + -то (-to).
тогда́-то • (togdá-to)
- just then
- that was the time when; that was just when
- Тогда́-то и ну́жно бы́ло э́то ей сказа́ть ― Togdá-to i núžno býlo éto jej skazátʹ ― That was just when you should have told her that.