NEWS

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theRefdate 1.1.0 (2026-10-16)

New: date format ("flavour") can be chosen once per session

• Until now the package worked on strings in the format "DD.MM.YYYY" only. It now supports three formats, called flavours:
  • "dmy": "DD.MM.YYYY" (default, identical to version 1.0.0)
  • "iso": "YYYY-MM-DD"
  • "iso_basic": "YYYYMMDD"
• New function setFlavour() selects the flavour for the whole R session. All functions then work on strings of that format. Calling setFlavour() again with a different flavour in the same session gives a warning, because two formats in one session usually indicate a mistake. The old identifiers "LP" (= "dmy") and "VK" (= "iso") are still accepted.
• flavour() returns the active flavour. It now returns "dmy" by default (version 1.0.0 returned "LP").
• jahr(), monat(), tag(), dateDiff() and dateAddMonths() have a new optional argument format that overrides the session flavour for a single call.

Unchanged: results without setFlavour()

If setFlavour() is never called, the package works in the format "DD.MM.YYYY" and returns the same results as version 1.0.0 for every valid input (day, month and year in the format, years 1000 to 9998, whole months). A test (tests/testthat/test-kompatibel-1.0.0.R) compares the results with values produced by the version published on CRAN.

Changed: errors instead of NA and instead of nonsense results

Version 1.0.0 answered invalid input with NA or with a malformed string. Version 1.1.0 stops with an error message that names the argument, its class and value, and the expected format.

• NA is now an error. jahr(), monat(), tag(), dateDiff() and dateAddMonths() no longer return NA for an NA, an empty string or a string that is not a date; they signal an error. Code that relied on NA being passed through (for example sapply() over a column with gaps) needs to filter those values first or wrap the call in tryCatch(). The same applies to a call without arguments.
• A string in a different format than the active flavour (for example an ISO date while the default is "DD.MM.YYYY") is an error.
• dateAddMonths() accepts whole months only (a number of length 1). A fractional number of months, which gave results like "01.01.5.2000", is an error.
• dateAddMonths() stops if the resulting year is outside 0 to 9999. Version 1.0.0 returned values such as "31.01.1000" for a result beyond the year 9999.
• The months are now added in a single step instead of recursively. Results for valid input are the same.

Changed: output format of dateAddMonths()

• The year in the result is always written with four digits, month and day with two digits ("01.01.0001" instead of "01.01.1"). For years from 1000 on nothing changes.

Documentation

• The vignette explains the flavours and setFlavour().
• Documentation of all functions describes the argument format.
• The help pages are now written in English (they were in German); the Language field in DESCRIPTION is en-US. Error messages are unchanged.

theRefdate 1.0.0 (2026-03-23)

• First CRAN release: date manipulation on character strings in the format "DD.MM.YYYY" with jahr(), monat(), tag(), dateDiff(), dateAddMonths() and flavour().