diff options
Diffstat (limited to 'lib/stdlib/src/calendar.erl')
| -rw-r--r-- | lib/stdlib/src/calendar.erl | 53 |
1 files changed, 53 insertions, 0 deletions
diff --git a/lib/stdlib/src/calendar.erl b/lib/stdlib/src/calendar.erl index ddc0666f77..57b7c28dee 100644 --- a/lib/stdlib/src/calendar.erl +++ b/lib/stdlib/src/calendar.erl @@ -28,6 +28,8 @@ gregorian_days_to_date/1, gregorian_seconds_to_datetime/1, is_leap_year/1, + iso_week_number/0, + iso_week_number/1, last_day_of_the_month/2, local_time/0, local_time_to_universal_time/1, @@ -70,6 +72,7 @@ -type second() :: 0..59. -type daynum() :: 1..7. -type ldom() :: 28 | 29 | 30 | 31. % last day of month +-type weeknum() :: 1..53. -type t_now() :: {non_neg_integer(),non_neg_integer(),non_neg_integer()}. @@ -77,6 +80,7 @@ -type t_time() :: {hour(),minute(),second()}. -type t_datetime() :: {t_date(),t_time()}. -type t_datetime1970() :: {{year1970(),month(),day()},t_time()}. +-type t_yearweeknum() :: {year(),weeknum()}. %%---------------------------------------------------------------------- @@ -172,6 +176,42 @@ is_leap_year1(Year) when Year rem 400 =:= 0 -> is_leap_year1(_) -> false. +%% +%% Calculates the iso week number for the current date. +%% +-spec iso_week_number() -> t_yearweeknum(). +iso_week_number() -> + {Date, _} = local_time(), + iso_week_number(Date). + + +%% +%% Calculates the iso week number for the given date. +%% +-spec iso_week_number(t_date()) -> t_yearweeknum(). +iso_week_number({Year, Month, Day}) -> + D = date_to_gregorian_days({Year, Month, Day}), + W01_1_Year = gregorian_days_of_iso_w01_1(Year), + W01_1_NextYear = gregorian_days_of_iso_w01_1(Year + 1), + if W01_1_Year =< D andalso D < W01_1_NextYear -> + % Current Year Week 01..52(,53) + {Year, (D - W01_1_Year) div 7 + 1}; + D < W01_1_Year -> + % Previous Year 52 or 53 + PWN = case day_of_the_week(Year - 1, 1, 1) of + 4 -> 53; + _ -> case day_of_the_week(Year - 1, 12, 31) of + 4 -> 53; + _ -> 52 + end + end, + {Year - 1, PWN}; + W01_1_NextYear =< D -> + % Next Year, Week 01 + {Year + 1, 1} + end. + + %% last_day_of_the_month(Year, Month) %% %% Returns the number of days in a month. @@ -377,6 +417,19 @@ dty(Y, D1, D2) when D1 < D2 -> dty(Y, _D1, D2) -> {Y, D2}. +%% +%% The Gregorian days of the iso week 01 day 1 for a given year. +%% +-spec gregorian_days_of_iso_w01_1(year()) -> non_neg_integer(). +gregorian_days_of_iso_w01_1(Year) -> + D0101 = date_to_gregorian_days(Year, 1, 1), + DOW = day_of_the_week(Year, 1, 1), + if DOW =< 4 -> + D0101 - DOW + 1; + true -> + D0101 + 7 - DOW + 1 + end. + %% year_day_to_date(Year, DayOfYear) = {Month, DayOfMonth} %% %% Note: 1 is the first day of the month. |