# Module `Os_date` Time zone and date management for Web applications. This module provides some useful functions to detect and manage time zones, print dates, etc. It's essentially a wrapper to [`CalendarLib.Calendar.t`](./../../calendar/calendar/CalendarLib-Calendar.md#type-t) through an abstract type and by using zone and date data provided by the browser. See `calendar` OCaml library for more information about `CalendarLib` module. Specifiers from `calendar` OCaml library are used: refer you to the official documentation (http://calendar.forge.ocamlcore.org/doc) to know the significations. ```ocaml type local_calendar ``` Type representing a local calendar. ```ocaml val to_utc : ?timezone:string -> local_calendar -> CalendarLib.Calendar.t ``` Convert a local calendar to a UTC calendar. Use the client's timezone unless the optional `timezone` argument is provided. ```ocaml val to_local : ?timezone:string -> CalendarLib.Calendar.t -> local_calendar ``` Convert any type of calendar to a local calendar. Use the client's timezone unless the optional `timezone` argument is provided. ```ocaml val now : ?timezone:string -> unit -> local_calendar ``` `now ()` returns the current date as a `local_calendar` value. Use the client's timezone unless the optional `timezone` argument is provided. ```ocaml val initialize : string -> unit ``` You can use `initialize timezone` to communicate the client's timezone to the client when the auto-initialization is disabled ```ocaml val user_tz : unit -> string ``` `user_tz ()` returns current user's timezone. ```ocaml val to_local_time : local_calendar -> CalendarLib.Time.t ``` Convert a `local_calendar` value to a `CalendarLib.Time.t` value. ```ocaml val to_local_date : local_calendar -> CalendarLib.Date.t ``` Convert a `local_calendar` value to a `CalendarLib.Date.t` value. ```ocaml val local_to_calendar : local_calendar -> CalendarLib.Calendar.t ``` Convert a `local_calendar` value to a `CalendarLib.Calendar.t` value. ```ocaml val local_from_calendar : CalendarLib.Calendar.t -> local_calendar ``` Convert a `CalendarLib.Calendar.t` value to a `local_calendar` value. ```ocaml val unknown_timezone : unit -> bool ``` `unknown_timezone ()` returns `true` if the timezone is unknown. Else returns `false`. ```ocaml val smart_time : ?now:local_calendar -> local_calendar -> string ``` `smart_time ~now date` returns a smart description of `local_date` comparing to `now` (default value of now is the current time when the function is called). It does the same job than [`smart_date`](./#val-smart_date) but « at %hour » is added at the end where %hour is computed from [`smart_hours_minutes`](./#val-smart_hours_minutes). ```ocaml val smart_date : ?now:local_calendar -> local_calendar -> string ``` `smart_date ~now local_date` returns a smart description of `local_date` comparing to `now` (default value of now is the current time when the function is called). Smart means - if `local_date` is the day before `now`, `"Yesterday"` is returned. - if `local_date` is the same day than `now`, `"Today"` is returned. - if `local_date` is the day after `now`, `"Tomorrow"` is returned. - if `now` and `local_date` has the same year, it returns the date in the format: `"%A %B %d"`. - else the year is added at the end in the same format than the previous case. ```ocaml val smart_hours_minutes : local_calendar -> string ``` `smart_hours_minutes date` returns the time in the format `"%I:%M%P"`. If the timezone is unknown, GMT is added. ```ocaml val smart_interval : ?now:local_calendar -> local_calendar -> local_calendar -> string ``` `smart_interval ?now start_date end_date` returns a smart description of `start_date` comparing to `end_date` of the year, month, day, hour and minutes (compared to [`smart_date_interval`](./#val-smart_date_interval), information about the hour and minutes is given). The year is not used if `start_date` and `end_date` or if `start_date` and `now` have the same year. The final output is the concatenation of `smart_start_date` and `smart_end_date` with a dash between them. `smart_start_date` and `smart_end_date` in in the format `"%B %d, %Y"` if year is needed and `"%B %d"` if not. ```ocaml val smart_date_interval : ?now:local_calendar -> local_calendar -> local_calendar -> string ``` `smart_date_interval ?now start_date end_date` returns a smart description of `start_date` comparing to `end_date` of the year, month and day (compared to [`smart_interval`](./#val-smart_interval), no information about the hour and minutes is given). The year is not used if `start_date` and `end_date` or if `start_date` and `now` have the same year. The final output is the concatenation of `smart_start_date` and `smart_end_date` with a dash between them. `smart_start_date` (resp. `smart_end_date`) is `start_date` (resp. `end_date`) in the format `"%B %d, %Y, %I:%M%P"` if year is needed and `"%B %d, %I:%M%P"` if not.