| Because the length of a month or year changes from one month or year to the next, ambiguities can arise when shifting a date by months and/or years. For example, what is the date one year after 2024-02-29? Is it 2025-02-28 or 2025-03-01? Or what is the date that is two months after 2023-12-31? Is it 2024-02-29 or 2024-03-02? There is no consensus on how to resolve this ambiguity, so the "ceiling" and "floor" modifiers (14 and 15) are available to let the programmer decide. If the next modifier after a time shift is "ceiling", then any ambiguity in the date is resolved by choosing the later date. The "floor" modifier resolves ambiguities by resolving to the last day of the previous month. The default behavior is "ceiling".
Looking... I can't find it with Google, but https://www.sqlite.org/lang_datefunc.html mentions it:
| Because the length of a month or year changes from one month or year to the next, ambiguities can arise when shifting a date by months and/or years. For example, what is the date one year after 2024-02-29? Is it 2025-02-28 or 2025-03-01? Or what is the date that is two months after 2023-12-31? Is it 2024-02-29 or 2024-03-02? There is no consensus on how to resolve this ambiguity, so the "ceiling" and "floor" modifiers (14 and 15) are available to let the programmer decide. If the next modifier after a time shift is "ceiling", then any ambiguity in the date is resolved by choosing the later date. The "floor" modifier resolves ambiguities by resolving to the last day of the previous month. The default behavior is "ceiling".