Maniphest tasks are identified with "monograms", like `T123`. Other major objects in other systems use other letters (`D` for Differential revisions, `F` for files, etc). See [[ object_name_prefixes | Object Monograms ]] for a full list.
Calendar has "E" reserved for it, but the UI doesn't reflect that. Particularly, these things should be supported:
- The main URI for an event should be `/E123`.
- The crumbs for an event should end in `> E123`.
- The page title for an event should be `E123 Event Name`.
- Typing `E123` in remarkup should link to the event.
- Typing `{E123}` should embed a longer reference to the event.
- Typing `E123` in global search should jump to the event.
- Mail about the event should identify it with `E123`.
Note that "E" used to mean "Conpherence Thread". We've mostly moved that to "Z" to let Calendar have "E", but there may be some remnants kicking around.