1979 - 1991
crazy to think how different VI is to TMP. The changes to the cast in just little over 10years (in TMP they looked pretty much the same as they did in season 3 of TOS, they looked bit older in II but it wasnt until III/IV they were starting to look their age) , how old fashioned/70s TMP was compared to VI or even II just 3years later or III 5 years on .. (each movie feels like a product if its era like they were charting the zeitgeist & often mirroring the popular movies of the time like Bond films do: TMP cold pre SW 70s scifi, II cold war action thriller/Alien, III has elements of sword&sorcery films/Lucas Star Wars/Spielberg Temple of Doom, IV fish out of water Croc Dundee comedy/BTTF timetravel, V the televangelist thing, & VI feels like the early 90s end of the cold war/Red October - then further on FC: Aliens meets Terminator, ST09: reboot like Batman/Bond, ID: TDK, Beyond: Avatar/Guardians/F&F )
I know 12years is a long time but consider recent stuff like the MCU and Craig Bond which feels fairly consistent in look/style from 1st film to last 15years later (then again if you look at the previous Bonds Connery/Moore its more similar to the star trek films)