The Markets in Financial Instruments Directive (MiFID) are in place to increase market stability and improve consumer protection. The latest version (MiFID II) comes into force on January 3rd 2018.

Companies will need to meet a range of new or tighter regulations covering Pre-trade, Execution and Post-trade data, with accurate record keeping of all transactions being key.

One of the tighter requirements is in Time Synchronisation in particular:

Trade and Transaction Reports: Articles 6, 7, 10 & 11
Full Audit Trail: Articles 25(1), 25(2) & 17(2)
Records of Services, Activities: Article 16(6)
Compliance with the maximum divergence requirements: Article 4

UTC Traceability has to be demonstrated – and for all electronic trading deals must be recorded to an accuracy of 100 micro-seconds (100 millionths), and due to the vagrancies of software in complex systems, this means that the time accuracy at the point of distribution in a trading centre probably needs to be close to 1 micro-second.

More info here