Android: NLP library for date recognition in string
Maybe too late, but you could have a look at HeidelTime. It is a Java library that can detect dates, times, durations and time sets in texts for many languages. The downside of HeidelTime is that it seems to be not maintained since 2018. Also, you need the TreeTagger tool in order to use it. But the README of HeidelTime explains the necessary steps quite detailed.

Another alternative or addition to HeidelTime would be defining several regular expressions of common date and time formats and find these in your input text.