Date Authority

Use the Date Authority service to interpret dates using FamilySearch. Read more about Normalized Date Formats.


Use this URI to interpret dates based on a date phrase as query parameters.

HTTP Method



The date phrase for which an interpretation is needed.
Note: Use the date.max.dates parameter of the Authorities Properties Authority service to obtain the maximum number of dates that you can include in one request.
The julian day number or astronomical date.
The language in which the date should be returned. The supported values are:
  • ar (Arabic)
  • be (Belarusian)
  • bg (Bulgarian)
  • ca (Catalan)
  • cs (Czech)
  • da (Danish)
  • de (German)
  • el (Modern Greek)
  • en (English)
  • es (Spanish)
  • et (Estonian)
  • fi (Finnish)
  • fr (French)
  • ga (Irish)
  • hr (Croatian)
  • hu (Hungarian)
  • in (Indonesian)
  • is (Icelandic)
  • it (Italian)
  • iw (Hebrew)
  • ja (Japanese)
  • ko (Korean)
  • lt (Lithuanian)
  • lv (Latvian)
  • mk (Macedonian)
  • ms (Malay)
  • mt (Maltese)
  • nl (Dutch/Flemish)
  • no (Norwegian)
  • pl (Polish)
  • pt (Portuguese)
  • ro (Romanian)
  • ru (Russian)
  • sk (Slovak)
  • sl (Slovenian)
  • sq (Albanian)
  • sr (Serbian)
  • sv (Swedish)
  • th (Thai)
  • tr (Turkish)
  • uk (Ukrainian)
  • vi (Vietnamese)
  • zh (Chinese)


Error Possible Causes Implemented
400 Bad Request: Generic client error or multiple client errors. Could be caused by:
  • Invalid parameter or parameter value
  • Requesting more dates in one query than the API supports. Use the Authorities Properties service to see current limits.
401 Unauthorized. The user has invalid credentials or the session ID is missing, invalid, or has expired. This error also appears if the query string contains multiple question marks or the the session parameter contains letters in an incorrect case. Yes
500 Server Error: A generic server error or multiple server errors occurred. If you get this error, please report it through You can also post it to the FamilySearch Developer Network (FSDN). Yes
503 Service Unavailable: FamilySearch or the service that you are using is not currently available. Or you are being throttled. Yes



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