Today is a good day for invoking Mercury

The moon is waxing and forms a good aspect with Mercury. The planetary hours for London, UK are (or were) 0722 – 0806; 1230 – 1314; and 1842 – 1958 this evening.

Planetary hours for the daytime can be calculated by taking the length of time between dusk and the preceding dawn and dividing by 12. The first hour (i.e. beginning at dawn) is always that of the planet after which the day of the week is named – it is in fact the reason why in ancient times the days of the week were named as they were. Hence: Sunday = Sun, Monday = Moon, etc. The rest of the hours follow the natural order of the planets, repeating after every seven: Saturn, Jupiter, Mars, Sun, Venus, Mercury, Moon.

The planetary hours for the night-time are calculated by dividing the time between dawn the following day and dusk the previous day by 12. (See, for example, here). The planets are assigned in the same order as the day hours, following straight on from the last hour which ended at dusk.