So, first here's the timeline by itself.

20X5

January: The federation Discovers a Metroid egg on SR-388, they bring it on their ship but before they can take it back home space pirates attack the vessel and steal the egg.

April: Metroid Zero Mission

August: Metroid Prime 1

20X6

January: Metroid Prime Hunters

April: Metroid Prime 2

October: Metroid Prime 3 Opening

November: Metroid Prime 3 >!Post PED!<

December: Metroid Federation Force

20X7

September: Metroid Samus Returns

September: Super Metroid

October: Other M Tutorial

20X8

May: Metroid Other M

20X9

March: Metroid Prime 4

20(X+1)0

June: Metroid Fusion

October: Metroid Dread

That sure is a timeline. But allow me to now explain some of my reasoning! Do be warned massive spoilers for the entire series. read ahead at your own risk.

MY REASONING

first things first. Some games do have canon years attached to them already, these are

20X5: Zero Mission (multiple manuals and Samus Returns intro)

20X6: Prime 3 (Fed Force intro), and Fed Force (Prime 4 scan)

20X9: Prime 4 (Prime 4 intro)

so, with that being said. let's talk about why i picked the specific months I did! going in order of the timeline

Zero Mission: in the Metroid Origin Manga, it is stated that the time between the federation discovering Metroid's on SR-388 and the start of Zero Mission

Sr-388... this is where the trouble began. Three months ago, the planet reclamation division reported an uncharted planet ad a group was sent to survey the area.

while the manga has many differences with the games. If we assume this time frame is accurate. With us knowing Metroid's were discovered in 20X5 then that forces Zero Mission to be at least in April (because 3 months prior would be January).

Metroid Prime 1: Thanks to the fall of Zebes logbook entry which is dated for Cycle 9.992.3 and a minor scan saying tempeture regulations were fixed after Cycle 12.112.4. We know that Prime 1 takes place at least 2.12 cycles after the events of Zero Mission.

we can then figure out how long a cycle is with the help of Metroid Prime 2! in Prime 2 it's stated that 8 days prior to the start of the game Federation soldiers went missing on Aether. according to the Prime 2 space pirate logs, the federation soldiers landed (and lost communication) on Aether in 7.013.6, and that Samus lands on the planet on 7.159.9. doing math that means 0.146 cycles = 8 days, which means that 0.01825 cycles = 1 Day!

so, if we divide 2.12 cycles by 0.01825, we get 116.16... which means that Prime 1 takes place around 4 months after Zero Mission, and since we placed Zero Mission in April that would make Prime 1 be sometime in August.

Metroid Prime Hunters: confirmed to be between Prime 1 and 2, so the month of January is merely just the exact halfway point between the two months lol.

Metroid Prime 2: There's a statement in Prime 3 from one of the space pirate logs that says

Phazon was discovered two stellar years ago, and since that moment, Command has been driven to control it all.

We can't place Prime 2 2 years after the discovery of Phazon since that would contradict Prime 3 and Fed Force's date of 20X6. However, this statement made me want to put Prime 2 as far as I physically could away from the discovery of Phazon. April is the last month it can possibly be before it contradicts Prime 3 being sometime in 20X6 as Prime 3 is stated in its manual to start 6 months after the events of Prime 2. This would place Prime 2 around 1 year after the discovery of Phazon.

Metroid Prime 3: Stated to start 6 months after Prime 2 in the Prime Trilogy manual (and supported in the Elysia logs though never fully stated)

Six months have passed since the events on the planet Aether.

then after a major story moment it is directly stated on screen that 1 month then passes. meaning with an April date for Prime 2 that places Prime 3 as starting in October and ending in November

Metroid Federation Force: We know it has to be the same year, and it's implied to not be immediately after Prime 3, which makes me feel at least 1 month has to pass. and luckily with a Prime 3 November end date. the month of December is fully available.

From this point further any future months purely become headcanon without much evidence.

Samus Returns and Super Metroid: since these two games take place back-to-back, they have to be in the same month. With Federation Force taking place in December the game has to be in at least 20X7. I personally feel it would take a while to get the Space Pirates on their last legs to the point Super becomes their last stand. Making it likely later in the year. personally picked September specifically because it was the month Samus Returns released in lol.

Metroid Other M: While the intro only takes place shortly after. the main game is implied to be super long after that

people's recollections of Metroids and Space Pirates grew nebulous over time relegated to a past concern of the galactic communities... Nothing more than a faded memory

This would take a while and would force Other M to be in 20X8 minimum when Super is in 20X7. 20X8 also seems fitting as it allows it not to have to but heads with Prime 4 in 20X9. As for why May? With how much motherhood is a running motif I thought putting it in the same month as Mother's Day was fitting.

Metroid Prime 4: Known to be in 20X9 because of its intro, then based on how the world guide >!seems to imply Sylux has been using his fusion mochtroids on bases for a few months now!< prior to the events of the game but still in the same year. March seems like a fitting month, it also gives a lot of room for future Prime games that may want to take place in 20X9 as well.

Metroid Fusion and Metroid Dread: In Metroid Fusion's English manual (and from what I can tell the Japanese manual as well) it's stated.

Sr-388, a vile former home of the Metroids, after so many years, the remaining creatures on this planet still seem to be trying to create a natural hierarchy without Metroids.

This sounds like it's been at least 3 years and potentially more since the events of Metroid 2. however, I also can't imagine it would take that long for the X to completely take over the planet once Metroids disappeared. which is why I'm putting it at exactly 3 years.

Dread doesn't seem to be too long after fusion judging by Samus' word choice of

Just when it all seemed over...

making me think it's only been a few months max, so because of this, I decided to place Dread in October (the month it came out and it feels fitting for the uber horror gameplay) and Fusion 4 months prior in June.

Conclusion

And that's the timeline! I hope it was an enjoyable read. I have debated on whether I should post this for a while now but decided to finally say "meh why not!" I hope you all have a lovely rest of your day!