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https://help.marriott.com/s/article/Article-24119

Marriott is tracked on a calendar year basis but the status applies until February of the next year.

For 2022 if you end with 38 nights you requalify for Gold status for all of 2023 and until February 2024.
If you have a higher status than Gold currently (e.g. if you have Platinum now), that will remain until February 2023 and then from February 2023 onwards you will have Gold.
In 2023, the counter resets so you will have 50 - 38 = 12 qualifying nights in January.

If you requalify for Platinum, for example, in June 2023, then you will have:
Platinum for January and February
Gold for March, April, and May
Platinum for June 2023 until February 2025

The system is designed so that if you are hitting the minimum threshold in December, for example, you get the full next year to enjoy the benefits. Obviously if you qualify early you get bumped up immediately.