Digit-only tags \d{3,7} does not start timetracking

[Spreadcat]

Hi,

I've got trouble using only digit tags.

The following command does not start time tracking

$ timew start 07:50 :adjust "foo" "bar" "1111"
Unrecognized date range: '<date> <duration>'.

Putting a character in front of it, fixes the issue

```shell
$ timew start 07:50 :adjust "foo" "bar" "b1111"
Unrecognized date range: '<date> <duration>'.

• The length of the number must be between two and eight digits.
• The position of the tag doesn't matter.

$ timew --version
1.9.1

[lauft]

Digit-only tags are currently interpreted by Timewarrior as dates.

Changing that requires some deeper modification of the command line handling.