A shield modification developed aboard Voyager during the Year of Hell that protected the ship against Krenim chroniton torpedoes and, unexpectedly, against the alterations to history made by Annorax's weapon ship.
Temporal shielding appears in the Voyager two-parter Year of Hell. Krenim chroniton torpedoes pass straight through ordinary shields because they are slightly out of phase with normal time. Seven of Nine and Tuvok recover the temporal variance from an unexploded torpedo lodged in the hull, an effort that costs Tuvok his sight, and the shields are retuned to match.
The new shields have a second effect. When the Krenim scientist Annorax erases whole species from history with his temporal weapon ship, Voyager is left unchanged, which draws his attention to it.
Janeway shares the technique with allied Nihydron and Mawasi ships for the final attack. She then deliberately lowers Voyager's own temporal shields before ramming the weapon ship, so that its destruction resets the timeline.