# Known limits These are the known limits of Koyomi 0.1. ## Browsers The browser tests run in Chromium, Firefox and WebKit (the engine of Safari), with the Playwright versions of these browsers, as desktop browsers, in the `en-GB` locale and the `Europe/Lisbon` time zone. They do not run in Safari on macOS or iOS, in a mobile browser, or with a screen reader. ## Weeks without `Intl` week data The first day of the week, the weekend and the first week of the year come from `Intl.Locale`'s week info (`getWeekInfo()`, or `weekInfo` in older engines). An engine without either uses a table built into the bundle, by region, from the CLDR data. The table may differ from a newer CLDR in a few regions. A locale with `-u-fw-` sets the first day in both cases, and the `first_day` attribute replaces it. A week picker always starts its weeks on Monday, and every week number is an ISO 8601 week, whatever the locale. ## Calendar systems * A picker in the Japanese calendar shows Japanese era years in the calendar and in its labels, but its segments take Gregorian numbers: the year is typed as `2027`, not as Reiwa 9. * The month, week and year pickers use Gregorian months and years. A `calendar` other than Gregorian, ISO, Japanese, Buddhist or ROC is replaced by the Gregorian calendar in these pickers. * The other calendars (Hebrew, Chinese, Islamic, Persian and so on) read their months from `Intl`. Where the browser has `Temporal`, the picker uses it to turn a typed date into a day; without it, the picker finds the day by a search through `Intl`, which gives the same days more slowly. `Temporal` is used only when the browser has it: the bundle has no polyfill. * A calendar that the browser cannot format falls back to Gregorian. The value that a picker posts is always an ISO 8601 date, whatever the calendar it shows. ## Plain words The typing box reads words in English, Portuguese, Spanish, French, German, Italian, Dutch and Japanese. A locale in another language reads English words, the locale's own month and weekday names (from `Intl`), and numeric dates in the locale's order. ASCII and full-width digits are read; other digits, such as Arabic-Indic, are read in the segments but not in the typing box. See the [Typing dates](typing.md) guide. ## Holidays `Koyomi.Holidays` lists national public holidays, computed by rule, for the countries of `Koyomi.Holidays.countries/0`. Regional, local and religious days that only some people keep are not listed, nor are days off by custom. The rules are those in force in 2026: changes since 2010 are followed, and earlier years follow the rules of 2010. One-off holidays are not listed. For the days off of a region or a business, write a `Koyomi.Holidays.Provider`. A picker gives the browser the holidays of a span of years: from the year of `:min` (else two years before today) to the year of `:max` (else three years after), and never more than ten years from today. Days outside that span show no holidays. ## Day content One `koyomi:days` event asks for at most 800 days. `Koyomi.Live.handle_days/4` answers a longer span with no days, and does not call the callback. A picker asks only for the days it shows that it has not asked for yet, in spans of at most a year. Days disabled in the day content are disabled only in the browser. Check them in the changeset with your own validation. ## A value posted is a value whole A picker posts only a value that it can read as a whole. A range posts when both of its ends are chosen; until then, the form keeps the previous value, and a range left half chosen when the popover closes is dropped. A date typed in segments posts when every segment has a value, or when every segment is empty. See the [Forms](forms.md) guide. ## Echoes of posted values A picker ignores a rendered value that equals one of the last eight values it posted, so that a slow render cannot undo what the person typed since. This list is cleared when a render brings the picker's current value. So a render that sets the field back to a value that the person posted a moment ago, for example after an undo in the LiveView, does not change the picker. Push such a value with `Koyomi.Live.push_value/3`, which the picker always takes. See the [Forms](forms.md) guide. ## Rules checked only on the server Two rules are checked only by the changeset: * `:min_count`: the several days picker lets the person choose fewer days, and the changeset refuses them. * The time of day of a `DateTime` or `NaiveDateTime` bound in `:min` or `:max`: the browser disables the days before the bound's date, and allows every time on that day. The time segments take any minute: `:step` limits the times of the time list, and a typed time off the step shows the rule's message under the field. ## Errors of the several days and recurrence pickers The several days and recurrence pickers have no segments, so an invalid value is marked only with the `koyomi-invalid` class of the field. No element of these pickers has `aria-invalid`, and `aria-describedby` given to them reaches no element. Show the error message next to the picker, where a person reading the form finds it. ## Times that the clocks skip or repeat A date and time picker with a `time_zone` shows a notice when the wall clock time is skipped (the hour the clocks go forward) or happens twice (the hour they go back). A skipped time is moved forward by the gap. A time that happens twice takes the first instant, or the second with `ambiguous: :later`, and the notice lets the person choose the other. On the server, `Koyomi.Changeset.cast_datetime/5` reads a time posted with an offset as that instant. A wall clock time posted with no offset (with JavaScript off) takes the first instant, or the second with its own `:ambiguous` option, and a skipped one gets the error `:gap`. A date and time picker with no zone posts the wall clock, and knows no clock changes. ## No range of dates and times `Koyomi.DateTimeRange` is an Ecto type for a span of time (a `tstzrange`), but there is no picker for it. Use two date and time pickers, one for each end, and cast their two values as a map with `"from"` and `"to"`. ## Ranges outside PostgreSQL `Koyomi.DateRange` and `Koyomi.DateTimeRange` store PostgreSQL range columns (`daterange`, `tstzrange`) by default. With `storage: :string` or `storage: :map` they store an ISO 8601 interval or a map in any database (SQLite, MySQL) and in embedded schemas, but the database sees text: a query for the ranges that hold a day, or that overlap, needs PostgreSQL's range columns, or the two ends in two fields. A range needs both ends: a range with one end is invalid, and a stored range with no bound (infinite) or an empty range reads back as `nil`. ## Recurrence rules `Koyomi.Recurrence` reads a subset of RFC 5545 `RRULE`: `FREQ` (`DAILY`, `WEEKLY`, `MONTHLY`, `YEARLY`), `INTERVAL`, `COUNT`, `UNTIL`, `BYDAY`, `BYMONTHDAY`, `BYMONTH`, `BYSETPOS` and `WKST`. Any other part is an error, among them `HOURLY`, `MINUTELY`, `SECONDLY`, `BYHOUR`, `BYMINUTE`, `BYSECOND`, `BYWEEKNO` and `BYYEARDAY`. A rule has no `DTSTART`, `EXDATE` or `RDATE`: the start is given apart, to `occurrences/3` and to the picker's `start`. The editor of the recurrence picker edits less than the type reads: how often, every how many, the weekdays of a weekly rule, the day of the month or the nth weekday of a monthly rule (both from `start`), and the end. A rule with other parts, such as `BYMONTH` or `BYSETPOS`, is shown in words, and its other parts stay until the person changes the frequency.