As you rule is secret, the answer is “probably”.
Recommended reading -
However, it seems you are extracting datetime from MQTT.
I would use transformation to get that data into a standard openHAB DateTime Item for convenience. If this is just about what you want to display, this would work better.
But if you need your original 50 string Items and want 50 just-the-time Items as well, you can create second MQTT channels that do different transformations to the same data but link to different Items.
If you tell us what you are trying to achieve it will help choose paths.