Metric was first introduced in 1799 (but abolished and then reinstated), the Imperial system in 1824. So both were in common use from the early 19th century.
How old is the metric system versus the imperial system?
https://en.wikipedia.org/wiki/Metric_system
According to this page the metric system was invented in 1799 in France.
The Imperial system was adopted in British empire in 1824
https://en.wikipedia.org/wiki/Imperial_units
English units were first used in about 1266 CE up until the Imperial system was adopted.
https://en.wikipedia.org/wiki/English_units
Korvo and Charles have answered your question but, of course, the metric system has been making its way across the globe since then. In Australia we switched to decimal currency in 1966 and the metric system from 1974.
All that is probably of little interest except that it allows me to say that in 1980 the breakfast announcer on a leading Sydney radio station announced that, in the spirit of metrication, they would in future be using metric time. He then said, "The time is now seven point two two."
After a few more "metric" time calls the station's switchboard was flooded from protesters (who couldn't work out that 7 point 2 2 was actually 7.22) and he was happy to announce that perhaps that had forgotten the date. It was April 1.