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LibWeb: Implement week_number_of_the_last_day

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stelar7
2023-12-10 18:13:03 +01:00
committed by Andrew Kaster
parent 6b79508c08
commit a72636ad8d
1 changed files with 12 additions and 2 deletions
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14
Userland/Libraries/LibWeb/HTML/HTMLInputElement.cpp
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@@ -831,10 +831,20 @@ static bool is_valid_time_string(StringView value)
}
// https://html.spec.whatwg.org/multipage/common-microsyntaxes.html#week-number-of-the-last-day
static u32 week_number_of_the_last_day(u64)
static u32 week_number_of_the_last_day(u64 year)
{
// FIXME: sometimes return 53 (!)
// https://html.spec.whatwg.org/multipage/common-microsyntaxes.html#weeks
// NOTE: A year is considered to have 53 weeks if either of the following conditions are satisfied:
// - January 1 of that year is a Thursday.
// - January 1 of that year is a Wednesday and the year is divisible by 400, or divisible by 4, but not 100.
// Note: Gauss's algorithm for determining the day of the week with D = 1, and M = 0
// https://en.wikipedia.org/wiki/Determination_of_the_day_of_the_week#Gauss's_algorithm
u8 day_of_week = (1 + 5 * ((year - 1) % 4) + 4 * ((year - 1) % 100) + 6 * ((year - 1) % 400)) % 7;
if (day_of_week == 4 || (day_of_week == 3 && (year % 400 == 0 || (year % 4 == 0 && year % 100 != 0))))
return 53;
return 52;
}