This paper reports on some experiments using different global clock mechanisms in distributed ledger technologies. Recently, using global clocks in distributed systems has become practical due to the progress of small atomic clock devices. However, current distributed systems such as typical distributed ledger technologies assume traditional loosely synchronized clocks. In this paper, we have implemented logical and physical global clock mechanisms in a distributed ledger system and investigated how different clock mechanisms influence the performance and scalability of distributed ledger technologies. When comparing these clocks, we found that the number of messages exchanged among the nodes is increased due to the number of the nodes required when using logical global clocks; thus, physical global clocks are more suitable than are logical global clocks for use in distributed ledger systems. We also found that the guarantee of transaction ordering based on the global time and the transaction throughput become a tradeoff in distributed ledger systems.