Annual Reports and information on time and frequency dissemination services

The Time Annual Report has evolved to offer more rapid and machine-readable access.

Up-to-date information is now accessible at:



Only the following three documents are updated annually:



Time Signals


Time Dissemination Services


Source of UTC(k)


BIPM Annual Report on Time Activities

BIH Annual Report (extract)


  • Since 2021, the Annual Report is no longer published as a full document: it was replaced by direct access to information available on the FTP server https://webtai.bipm.org/ftp/pub/tai/, also available on https://webtai.bipm.org/database/ and in the above files.

  • Since 2009 only electronic versions of the Annual Report have been published (on the internet), giving easy access to individual sections and tables.

  • Until 1987 the Bureau International de l'Heure (BIH) was responsible for the maintenance of UTC, and published all relevant information in the BIH Annual Report.