The fasting of expiations: such as the expiation for an oath, for declaring one's wife as unlawful (zihar), for killing, and for breaking the fast in Ramadan, requires the intention to be made at night, or an intention concurrent with the dawn; this is because these fasts are not specified, so the intention must be made to specify them, as explained in the book "Al-Waqayah" p. 234, and "Umdat Al-Ri'ayah" 1: 307. If one fasts with the intention after dawn, it will be considered voluntary, and he must make up this voluntary fast if he invalidates it.