Not sure what the issue is without seeing your code. Please post your code or a sample which shows what is going on. This link I found by doing a search on "chrono":
https://community.particle.io/t/chrono-no-such-file-or-directory/56870
In general, chrono literals can be found here in the docs:
https://docs.particle.io/reference/device-os/api/chrono-literals/chrono-literals/