https://www.rfc-editor.org/rfc/rfc5545#section-3.1:

Lines of text SHOULD NOT be longer than 75 octets, excluding the line break. Long content lines SHOULD be split into a multiple line representations using a line "folding" technique. That is, a long line can be split between any two characters by inserting a CRLF immediately followed by a single linear white-space character (i.e., SPACE or HTAB). Any sequence of CRLF followed immediately by a single linear white-space character is ignored (i.e., removed) when processing the content type.

The fold function splits a string across graphemes if the byte-size of the substring will exceed the max_size. It then adds a CRLF and an empty space at the split-point.

Parse a timedate text into DateTime.

Parse a timedate text into DateTime.

Splits a long line into several lines starting with a space.