In some places in iroha_data_model, structures use Duration for data which doesn't mean a span of time, but actually means a timestamp. Examples:

• start: https://github.com/hyperledger/iroha/blob/4362c9427fa8b4090676ac46e8171ef5f1995ff6/data_model/src/events/time.rs#L100-L105
• since: https://github.com/hyperledger/iroha/blob/4362c9427fa8b4090676ac46e8171ef5f1995ff6/data_model/src/events/time.rs#L126-L131

These fields are timestamps, not time spans.

I propose to use a structure that is designed specifically for timestamps, e.g. chrono::DateTime.