Clarify wording on dates

[daniellandau]

The previous wording could be understood to mean that completion date is mandatory if and only if creation date is also included.

[andoresuperesu]

Wouldn't the completion date be always optional also? I mean, the format doesn't require a completion date ever. The wording should be something like: If you've used the prepended date (optional), you can use that with the completed date (also optional) to calculate how many days it took to complete a task. Do I understand it correctly?

[JMoerman]

The wording should be something like: If you've used the prepended date (optional), you can use that with the completed date (also optional) to calculate how many days it took to complete a task.

I think this is slightly better: If you've used the prepended date (optional), you can use that with the completed date (which is in that case required) to calculate how many days it took to complete a task.

For finished tasks a completion date is required if a creation date is present. See:

If you’ve prepended the creation date to your task, on completion it will appear directly after the completion date. This is so your completed tasks sort by date using standard sort tools.

This part not only gives information on where the location of the completion date, but it also points to the completion date being required if a creation date is present. Otherwise, sorting tasks by date completion date wouldn't work. This together with

With the completed date (required), if you've used the prepended date (optional), ...

leads me to believe that a completion date is required only when a creation date is present.

I do not think a completion date is required in all cases, which is the way @daniellandau explains it in JMoerman/Go-For-It#56, as:

1. Both creation date and completion date are explicitly optional according to the spec.
2. If a completion date was mandatory a creation date would be mandatory as well as, according to the specification, a creation date must be present if a completion date is.

In any case, I agree that

With the completed date (required), if you've used the prepended date (optional), you can calculate how many days it took to complete a task.

should be replaced with a less confusing sentence.

[andoresuperesu]

Please rewrite to resemble the sentence as discussed: If you've used the prepended date (optional), you can use that with the completed date (which is in that case required) to calculate how many days it took to complete a task.
As that would be the most clear paragraph. Do you agree?

[clach04]

I agree the existing language is poorly worded and ambiguous. In addition, if we assume for a moment that completion date is mandatory, then that makes the todo.txt specification incompatible with existing todo.txt files (including the sample http://todotxt.org/todo.txt). Version 1.4 of todo.sh did NOT add completion dates. Sadly some history has been lost due to bitrot and hosting services disappearing since 2006.

too-much-todotxt/spec#15 includes references and previous discussions on this topic.

[clach04]

My attempt to resolve https://github.com/too-much-todotxt/spec/blob/main/The-Todo.txt-Format.md based on 2006 specification and 2009 changes to todo.sh (which leaked into spec).