Date/Time Names

Textual Fields

Certain calendar fields can have both numeric and textual forms. The textual forms can vary in length, from narrow to full. Some languages also need two different forms of these textual forms according to whether they used for formatting, or stand-alone. For more information, see Date/Time Patterns.

For names of eras, months, weekdays, and day periods, use the capitalization that would be appropriate in the middle of a sentence; the  <contextTransforms> data can specify the capitalization for other contexts. For more information, see Capitalization.


There are only two values for an era in a Gregorian calendar.  The common presentation of these era names in English are the more religious forms "BC" (Before Christ) and "AD (Anno Domini)" - from the Latin for "The year of our Lord". The secular equivalents of these two era names are "BCE" (Before Common Era) and "CE" (Common Era).

As of CLDR 24 it is now possible for a locale to supply both forms, if both are used in the locale. You will need to consider whether the religious (BC/AD) form or the secular (BCE/CE) form is more commonly used in your language, and make the most common form the default form (code 0, 1). The alternate form, if used, can be provide under the entries for codes 0-variant, 1-variant. If your locale does not commonly use an alternate form, do not provide any entries for these.

Other calendars have a different numbers of eras. The names for eras are often specific to the given calendar, such as the Japanese era names. You only typically need to translate these if the calendar in question is in common use in one of the countries that uses your language.

Months of the Year

This field is one of the months of the year, such as January or February.

Days of the Week

This field is one of the days of the week, such as Sunday or Monday.

Day Periods (AM and PM)

  1. You will be translating codes that may have no English equivalent.
    • For example, Malayalam has the code morning2, which doesn’t exist in English.
  2. The goal is to make sure that the wide format and wide stand-alone forms are correct.
    • The short and narrow forms do not need to be supplied.
  3. The time span associated with each code is different for different languages!
    • To see what the time-spans are for your language, hover over the value.
    • You should see something like the following:
    • It shows the time span (with a 24 hour clock) for the code, and then an example (for the format codes).
      • You can also go to the web page Day Periods, and look for your language.
      • For example, for Malayalam, you would go to ...day_periods.html#ml , and see that morning2 is the period that extends from 06:00 to 12:00.
  4. The format version will be substituted into a time format, and should contain whatever inflections/prepositions are necessary for that.
    • For example:
        Code English German Russian
      Standalone morning1 morning Morgen утра
      Formatting morning1 in the morning morgens утро
      formatting example morning1 10:00 in the morning 10.00 morgens 10:00 утра
  5. For more about how this works, be sure to read the following section.

DayPeriods are spans of time during the day. There are two forms for each possible period:
  • stand-alone: used to label a particular period, such as "morning".
  • format: used in combination with a specific time, such as "12 noon" or "7 in the morning".
The codes may also be used—like plural categories—to select messages based on the day period. For example, an email program might use them to select among messages like: "arrived last night" or "arrived this morning".

In all of the Span examples below, the times are 24 hour starting at 00:00 (midnight). The span does not actually include the second number of the range. For example, 05:00-08:00 is really 05:00-07:59:59.999... 

There are two types of day periods, fixed and locale-specific.

Fixed Periods

The fixed periods have the same definition in each language. The codes am and pm must always exist, even if your language always uses 24 hour time and doesn't use am/pm in any patterns (they are required for testing). So use the best term you can. As long as the 24 hour symbol (H) is used in the patterns, they won't actually show up in formatted times and dates.

Noon or midnight don't have to be present if the precise terms don't exist in your language. For example, many languages don't have a special term for precisely 12:00 noon. They may have a term for "midday" that spans from (say) 11:00-13:00, but not have unique term for exactly 12:00 noon. Such a language should not have a code for noon show up in the Survey Tool.

In formatting, where your language has a term for midnight, it is used instead of the term for am for the point in time 00:00 (= 24:00). Similarly, where your language has a term for noon, it is used  instead of pm for the point in time 12:00.

Code English Examples Span
am am 00:00–12:00 (noon)
pm pm 12:00–24:00
midnight midnight The point in time at precisely 00:00 midnight
noon noon The point in time at precisely 12:00 noon

Locale-Specific Periods

These mark approximate periods in the day, and those periods differ between languages. The codes are arbitrary, and don't have to match the English meaning for your language: the important feature is the time span. The spans are approximate; in reality they may vary with the time of year (they might be dependent on sunrise), or context (someone might say they went to bed at 2 at night, and later one say that they woke up at 2 in the morning). 

For a list of the spans defined in CLDR, see Day Periods. If you think the rules are wrong (or missing) for your language, please file a ticket and supply the missing information. Here are examples for English and Chinese.

Code English Span Chinese Span
morning1 morning 06:00–12:00 早上 05:00-08:00
morning2 unused
上午 08:00-12:00
afternoon1 afternoon 12:00–18:00 中午 12:00-13:00
afternoon2 unused
下午 13:00-19:00
evening1 evening1 18:00-21:00 晚上 19:00-00:00
evening2 unused
night1 night 21:00–06:00 凌晨 00:00-05:00
night2 unused

Narrow Date Fields

The narrow date fields are the shortest possible names (in terms of width in common fonts), and are not guaranteed to be unique. Think of what you might find on a credit-card-sized wallet or checkbook calendar, such as in English for days of the week:


Cyclic Name Sets

Cyclic name sets are used in calendars where naming cycles are used for naming years, months, days, times of day or zodiacs. For example, the Chinese and Hindu calendars each use a 60-name cycle for naming years. Each cyclic name set has stand-alone and format textual forms of varying lengths, similar to months or days.

Month Patterns

For lunar calendars that can have months added or removed from the usual set of months in a year, month patterns are used to rename the affected months or the months around them.

Date Field Names

The date field name are used in user interfaces, such as a table used for inputting values.

Year       1942       
Month ...
Day ...

The grammatical form should be whatever is typical for such isolated or stand-alone cases: generally it will be nominative singular, titlecase (first letter capitalized).

Relative Date Names

Some dates can be specified by giving relative names, such as "this month", "last month" or "next month". For example, if today is Jan 10, then this month is January, last month was December, and next month is February. Thus:

Category English Examples Meaning
next X next month The event occurs in the next calendar month (day, etc).
this X this month,
The event occurs in the current calendar month (day, etc).
last X last month,
The event occurs in the immediately last month (day, etc).

  • There is a difference between unit patterns (see Pluralssuch as "1 year ago" and relative names such as "Last Year". The phrase "1 year ago" has more of sense of a duration. For example, on January 2nd, you could refer to an event on December 30th as "Last Year". You couldn't refer to it as "1 year ago".
  • Some languages have a special word for "The day before yesterday", which may also be displayed for translation.
When listing calendar events, or when emails arrived, an interface may abbreviate dates using relative names. In the following list, the events up to 2 months ago are listed with explicit dates, while the closer ones use relative dates. These names might be used in various contexts and the new guidance is that they should be capitalized as appropriate for the middle of a sentence. They can be programmatically capitalized (using the contextTransform data) for different contexts, such as for listing in a menu of column of an interface. Here is how these might be used in a listing of emails:

From Subject Date
Rick Re: Meeting in February 12:15
Tom, Sarah,… Avoiding taxes Yesterday
Nicole Investment opportunities in Germany? 4 days ago
Rick Meeting in February Last Month
Jane New Year's Eve Party! Dec 12, 2009

Relative Day-of-the-Week Names

Some dates can be specified by giving relative names, such as "last Saturday", "this Saturday", or "next Saturday". The distinction between 'this' and 'next' may not be present in your language, thus they may have the same translation.

Category English Examples Meaning
next X next Saturday The first Saturday after today, if it is in the following week.
this X this Saturday The first Saturday after today, if it is in the current week.
last X last Saturday The first Saturday before today.

For example, if today is Wednesday, then last Saturday was 4 days ago. This Saturday is in 3 days, and next Monday is in 5 days.

Week of

There are a number of patterns like “the week of {0}” used for constructions such as “the week of April 11, 2016” or “the week of April 11–15”. The placeholder can be a full or partial date. There is a related date pattern that it should be as consistent with as possible.

<dateFormatItem id="MMMMW" count="one">'week' W 'of' MMM</dateFormatItem>