London Welsh Centre was introduced in 1925. When it reappeared after the Second World War in October 1946 it was called "Y Ddinas". Some idea of the range of activities at the London Welsh Centre in the post war years can be gathered from the announcement in "Y Ddinas" for just one month, January 1948. The Centre was the venue for three dances, two nights of community singing, a concert, two whist drives and an "at home". The Centre’s magazine is now published quarterly alongside regular newsletters by email. Welsh language classes have been held more or less continuously at the London Welsh
Month on the initial approximation that 2 lunations last 59 days: a 30-day full month followed by a 29-day hollow month — but this is only roughly accurate, and eventually needs correction by using larger cycles, or the equivalent of leap days. Additionally, the synodic month does not fit easily into the year, which makes accurate, rule-based lunisolar calendars complicated. The most common solution to this problem is the Metonic cycle, which takes advantage of the fact that 235 lunations are approximately 19 tropical years (which add up to not quite 6940 days). However, a Metonic calendar will drift against the