FIFA rankings are updated after each recognised international window. As a result, they are usually changed a few times a year based on the FIFA schedule.
The next FIFA international window is March 20–28, so the next FIFA rankings will be released sometime in early April.
Here are the international windows on the 2023 FIFA match calendar and the games that can be played in each one. The windows apply to all confederations unless otherwise specified.
March 20-28 (2 matches)
June 12-20 (2 matches)
June 16-July 16 (AFC only — Asian Cup)
June 26-July 16 (CONCACAF only — Gold Cup)
September 4-12 (2 matches)
October 9-17 (2 matches)
November 13-21 (2 matches)

How FIFA rankings are calculated

Since 1992, FIFA has kept track of the ,FIFA men's world rankings
which are based on a point system. The method for calculating FIFA rankings was officially changed in August 2018.
This new system works by adding or subtracting points from a team's previous total based on results.
A country's team point total is influenced by the calibre of opponent a team faces. For example, beating a team ranked inside the top 10 will result in more points being gained than defeating a team ranked outside the top 20. The expected result of the game will also impact the number of points gained.
Specific games are given more weight, too. So a team will get more points if they win a World Cup match than if they win an international friendly.
Matches decided by penalty shootouts are not a straight win or loss for either team. Losing teams are given the same points as for a draw, while winners only get points equivalent to half a win. Losing knockout round matches in final competitions also doesn't result in teams losing any points.
Here's a calculation example provided by FIFA:
Team A has 1300 points before the match and wins a continental qualifier against team B that has 1500 points
For team A the formula is: P=1300+25*(1–(1/(10 exp (-(1300–1500)/600) +1)))
For team B the formula is: P = 1500+25*(0- (1 / (10 exp (-(1500-1300)/600) + 1)))
Thus, team A wins the match with 17 points and has P = 1317 pomatch.after the match
Team B loses the same amount of points and thus ends up with 1483 points after thematch.h

FIFA rankings points system

If the above example has you scratching your head, you're not alone. But understanding the points system a bit better should help with that.
The "importance co-efficient plays a big part in determining just how many ranking points a team can earn from each fixture and is as follows:
5 – friendlies played outside the International Match Calendar windows
10 – friendlies played within the International Match Calendar windows
15 – UEFA Nations League matches (group stage)
25 – UEFA Nations League matches (playoffs and finals), Confederations' final competitions qualifiers, FIFA World Cup qualifiers
35 – Confederations' final competitions matches (before quarter-finals)
40 – Confederations' final competitions matches (quarter-finals and later)
50 – FIFA World Cup matches (before quarter-finals)
60 – FIFA World Cup matches (quarter-finals, semi-finals, third place play-off and final)
Then, the result of that match is added to what was expected to find out what percentage of the above points are given.
Source: Football Arroyo