The last day refers especially to the time of resurrection and judgment at the end of the age. In John 7:37 it also denotes the closing day of the Feast of Tabernacles.
Definition
The last day is the time of resurrection and judgment at the end of the age. It may also refer to the closing day of the Feast of Tabernacles.
Biblical Usage
Jesus repeatedly uses “the last day” for resurrection and judgment. In John 7:37, “the last day, the great day of the feast,” denotes the eighth day of the Feast of Tabernacles.
Historical Background
The eighth day was observed as a Sabbath. The water libation performed on other days was not made on this closing day.
Historical Bible Dictionaries
International Standard Bible Encyclopedia (ISBE)
<p>(he eschate hemera): Repeatedly used by Jesus in Joh 6:39,40,44,54; 11:24; 12:48, for the day of resurrection and judgment (see ESCHATOLOGY OF THE NEW TESTAMENT). Compare the usage in the Old Testament (Isa 2:2; Mic 4:1) and the New Testament (Ac 2:17; 2Ti 3:1; 2Pe 3:3; 1 Joh 2:18; Jude 1:18) of "last days" and "last time" to denote the Messianic age.</p><p>See LATTER DAYS; LAST DAYS; LAST TIME.</p><p>In Joh 7:37, "the last day, the great day of the feast" refers to the eighth day of the feast of Tabernacles. This closing day was observed as a Sabbath (Le 23:36). On it the libation of water made on other days was not made; hence, the allusion of Jesus to Himself as the Giver of the living water.</p><p>James Orr</p>