At 4:36 behind Sapphire's shoulder, you can see a prominent jar of THYME on the shelf. A nod to the theme of this assignment.
The date on the cornerstone with the name Jed Mace is given as 2 Febrvary 1736. This was a Monday in the Old Style Julian Calendar used in the United Kingdom up to September 1752. As a matter of fact, that same date was Monday the 13th of February, 1736 in France, Italy, Spain, and other nations that had adopted the Gregorian Calendar. Thus, it was the same day of the week, but eleven days further on (later) in time for those on the Continent. This is because the British did not adopt the Gregorian Calendar when the Catholic nations of Europe did so in October 1582. This difference in dates lasted from then for the next one hundred and seventy years - one wonders whether Sapphire and Steel could have fixed that little anomaly in time.