R: Format a Datetime object: ISO 8601, RFC 2822 or RFC 3339

iso8601 {anytime} | R Documentation

## Format a Datetime object: ISO 8601, RFC 2822 or RFC 3339

### Description

ISO 8601, RFC 2822 and RFC 3339 are a standards for date and time representation covering the formatting of date and time (with or without possible fractional seconds) and timezone information.

### Usage

    iso8601(pt)

    rfc2822(pt)

    rfc3339(pt)

    yyyymmdd(pt)

### Arguments

`pt` | A `POSIXt` Datetime or a `Date` object

### Value

A character object formatted according to ISO 8601, RFC 2822 or RFC 3339

### ISO 8601

ISO 8601 is described in some detail in https://en.wikipedia.org/wiki/ISO_8601 and covers multiple date and time formats.

Here, we interpret it more narrowly focussing on a single format each for datetimes and dates. We return datetime object formatted as ‘2016-09-01T10:11:12’ and date object as ‘2016-09-01’.

If the option `anytimeOldISO8601format` is set to `TRUE`, then the previous format (with a space instead of ‘T’ to separate date and time) is used.

### RFC 2822

RFC 2822 is described in some detail in https://www.ietf.org/rfc/rfc2822.txt and https://en.wikipedia.org/wiki/Email#Internet_Message_Format. The Date and Time formating cover only a subset of the specification in that RFC.

Here, we use it to provide a single format each for datetimes and dates. We return datetime object formatted as ‘Thu, 01 Sep 2016 10:11:12.123456 -0500’ and date object as ‘Thu, 01 Sep 2016’.

### RFC 3339

RFC 3339 is described in some detail in https://tools.ietf.org/html/rfc3339 It refines both earlier standards.

Here, we use it to format datetimes and dates as single and compact strings. We return datetime object formatted as ‘2016-09-01T10:11:12.123456-0500’ and date object as ‘2016-09-01’.

### YYYYMMDD

This is a truly terrible format which needs to die, but refuses to do so. If you are unfortunate enough to be forced to interoperate with code expecting it, you can use this function. But it would be better to take a moment to rewrite such code.

### Author(s)

Dirk Eddelbuettel

### References

https://en.wikipedia.org/wiki/ISO_8601, https://www.ietf.org/rfc/rfc2822.txt, https://en.wikipedia.org/wiki/Email#Internet_Message_Format, https://tools.ietf.org/html/rfc3339

### Examples

    iso8601(anytime("2016-09-01 10:11:12.123456"))
    iso8601(anydate("2016-Sep-01"))

    rfc2822(anytime("2016-09-01 10:11:12.123456"))
    rfc2822(anydate("2016-Sep-01"))

    rfc3339(anytime("2016-09-01 10:11:12.123456"))
    rfc3339(anydate("2016-Sep-01"))

    yyyymmdd(anytime("2016-09-01 10:11:12.123456"))
    yyyymmdd(anydate("2016-Sep-01"))

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