Recent extensions to standardised date notation in
ISO 8601-2_2019(E)
create space for unspecified, uncertain, and approximate dates,
as well as succinct representation of ranges of dates.
These functions create and validate a new date class for R
that can contain and parse these annotations,
and are not typically user-facing.
Please see as_messydate() for the user-facing coercion function.
new_messydate(x = character())
validate_messydate(x)A character scalar or vector in the expected "yyyy-mm-dd" format
annotated, as necessary, according to ISO 8601-2_2019(E).
Object of class mdate
Unspecified date components, such as when the day is unknown,
can be represented by one or more Xs in place of the digits.
The modifier * is recommended to indicate that the entire
time scale component value is unspecified, e.g. X*-03-03,
however this is not implemented here.
Please be explicit about the digits that are unspecified,
e.g. XXXX-03-03 expresses 3rd March in some unspecified year,
whereas 2003-XX-03 expresses the 3rd of some month in 2003.
If time components are not given, they are expanded to this.
Approximate date components, modified by ~,
represent an estimate whose value is asserted
to be possibly correct.
For example, 2003~-03-03
The degree of confidence in approximation
depends on the application.
Uncertain date components, modified by ?,
represent a date component whose source is considered
to be dubious and therefore not to be relied upon.
An additional modifier, %, is used to indicate
a value that is both uncertain and approximate.
These functions also introduce standard notation
for ranges of dates.
Rather than the typical R notation for ranges,
:, ISO 8601-2_2019(E) recommends ...
This then can be applied between two time scale
components to create a standard range between
these dates (inclusive), e.g. 2009-01-01..2019-01-01.
But it can also be used as an affix,
indicating "on or before" if used as a prefix,
e.g. ..2019-01-01,
or indicating "on or after" if used as a suffix,
e.g. 2009-01-01...
And lastly, notation for sets of dates is also included.
Here braces, {}, are used to mean "all members of the set",
while brackets, [], are used to mean "one member of the set".
messydate