Allow easy combining of day and time

I have wondered about this already in taskwarrior, but here this is even much more important:
There are shortcuts for both date and time, but combining them is not easily possible. For example, if I want to specify that a task was stopped yesterday, I either need to calculate the relative hours or specify the full date, which is quite tedious. I would love to have a syntax like `yesterdayT2100` or similar - basically allowing me to combine any date and time format.

Further examples:
```
monT09:00Z
eomT1800
```