pub const AT: &str = "X-SIOUL-AT";Expand description
A time given to a task for one day by a drag in the day view (Task::at),
in UTC, as Sioul wrote it before time blocks: read still, never written
(a task is pinned to a time by a block, an event every calendar shows,
blocks). Not DTSTART: RFC 5545 wants DUE of DTSTART’s value type and
after it, and CalDAV servers that check (Sabre: Nextcloud) refuse a task
whose start has a time while its date asked is a date, or has passed.