Guardians of the Galaxy movies are a little different, however; because they're set in space, they tend to feel more self-contained, and less concerned with events on Earth.
Still, the events of Thanos snap his fingers and erased half the living beings in the universe, only for them to be brought back five years later - affected everyone. According to Captain Marvel, the same chaos seen on Earth affected every star system. When the Guardians left Earth in Avengers: Endgame, now ed by Thor, they'd have gone out into a cosmos still in chaos after the abrupt and unexpected restoration of those who had been lost. That naturally means there should be further repercussions from these events in Guardians of the Galaxy Vol. 3, especially given the film was originally supposed to kick off Phase 3.
Writing on Twitter, the MCU timeline. According to Gunn, there are "a couple years between Endgame & Vol 3." Given Avengers: Endgame's five-year time jump meant the film ended in October 2023, that would mean Guardians of the Galaxy Vol. 3 is sometime in late 2025. Gunn notes he's not aware of the placement of other MCU Phase 4 films and TV shows, but it's entirely possible this will be the furthest forward in the MCU timeline at the point of release.
Most viewers tend to assume Marvel's timeline is solid and unflexible. In reality, the studio appears to give writers and directors a lot of creative freedom and room to maneuver, meaning the timeline is rather more dynamic than audiences tend to realize. Gunn's observation is important in dating the cosmic Guardians of the Galaxy Holiday Special, and of course Guardians of the Galaxy Vol. 3 itself. It means these three take place over a two-year period, defining that particular branch of the MCU timeline.
This does, of course, probably mean the Disney+ timeline will be proven wrong when it comes to Thor: Love & Thunder. This has been placed after Ms. Marvel, meaning it is late 2025. However, the Groot of Thor: Love & Thunder hasn't grown at all since Avengers: Endgame, and he's confirmed to have changed appearance by the time of the Guardians of the Galaxy Holiday Special (and may well change again by the time of Guardians of the Galaxy Vol. 3). It's probably better to place Thor: Love & Thunder in 2024 instead.
Source: James Gunn