In some fashion, Maniphest tasks have to have due-dates for the tool to be acceptable for use in most industries.
Without this feature Phabriactor's user-base is restricted to only people working on pure software while also using an agile method (subset of a subset).

@Quazil, Maniphest Tasks support Custom Fields, which support dates. They just don't show on a calendar, but you can set a due date today.

I've recently found myself wishing for couple kinds of functionality that would connect calendar and maniphest:

• "due date" for tasks,
• recurring tasks (just like events)
• age-based priority for tasks (dunno if calendar would be involved, but i've seen some instances of similar FRs popping up)

First two seem like good candidate for herald rules, however it seems like presently it's impossible to create rule like:
For recurring:
Condition: Calendar Event ID matches Exxx AND Calendar Event Started/Stopped
Action: Create Task (or execute script that would create task)

For Due Date:
Condition: Calendar Event ID matches Exxx AND Calendar Event Started/Stopped
Action: Do nothing
Rule2:
Condition: Another herald rule matches [rule above] AND task matches Txxx AND status is "open"
Action: Change priority to "Unbreak Now" AND Send Email To "PR"

I'm not versed enough in Herald, but i think what I described is at least partially OK 😉 It seems that what prevents one form making similar rules is that Herald can't build rule based on object name/id and calendar events do not expose state for herald.

Something that would be useful to us would be the ability to create, or probably better, assign a task, as it nears a due date. E.g. we may set up a task due in a year's time, and anticipate working on it two months before it is due. It would be great to be able to schedule the task to be assigned on a particular date, and perhaps moved on a workboard. I don't think this would need to be any more complicated than a Herald action that runs at a particular date/time rather than in response to some other action. I'm not familiar with what Calendar can already do, as we don't have prototype applications turned on for our install, so apologies if this is already possible. I just thought I would mention this use case here for future reference.

The recurring and due date use cases in the previous comment would also be useful to us. I would prefer something more natural for the formulation, though, e.g. for tasks:

• when [Father Time] [reaches] value in [Due Date] (or other selected field), [Assign to] [ben].
• when [Father Time] [is one week before] value in [Due Date] AND [Status] is [any open status], [Set priority] to [High].
• when [Father Time] is [one month after] value in [Creation Date] AND [Status] is [any open status], [Send email notification] to [manager].

It would be great if task Due Dates (or other date fields, conceivably creation date could also be useful) could (optionally) appear on a calendar.

In T7930#215278, @isfs wrote:

Something that would be useful to us would be the ability to create, or probably better, assign a task, as it nears a due date. E.g. we may set up a task due in a year's time, and anticipate working on it two months before it is due. It would be great to be able to schedule the task to be assigned on a particular date, and perhaps moved on a workboard. I don't think this would need to be any more complicated than a Herald action that runs at a particular date/time rather than in response to some other action. I'm not familiar with what Calendar can already do, as we don't have prototype applications turned on for our install, so apologies if this is already possible. I just thought I would mention this use case here for future reference.

The recurring and due date use cases in the previous comment would also be useful to us. I would prefer something more natural for the formulation, though, e.g. for tasks:

• when [Father Time] [reaches] value in [Due Date] (or other selected field), [Assign to] [ben].
• when [Father Time] [is one week before] value in [Due Date] AND [Status] is [any open status], [Set priority] to [High].
• when [Father Time] is [one month after] value in [Creation Date] AND [Status] is [any open status], [Send email notification] to [manager].

It would be great if task Due Dates (or other date fields, conceivably creation date could also be useful) could (optionally) appear on a calendar.

I am looking for exact this functionality. This would provide us the possibility to do generic project management and not only agile software development using phabricator.