Hi, I recently I have implemented the Time Model for the nRF5 SDK for Mesh and happy to share my implementation here: https://github.com/hashing-cell/BLE_Mesh_Time_model
Hopefully this may be helpful to someone down the line who uses the nRF5 SDK for Mesh, since that SDK does not have a Time Model implementation and it will not be added since its in Maintenance Mode.
Note that there is no persistent storage in this implementation, storing the time states is left up to the user.
Cheers
