Both mayoral and shrieval regular terms of office have always begun in the autumn of one year and run until the autumn of the next year, although never coinciding. From at least the early 14th century until 1752, the mayor's term of office began on 28--29 October and ended on the same dates one year later, although in some periods the ceremonies of 29 October were postponed to a later (usually the next) day when 29 October fell on a Sunday. (See Liber Albus, comp. J. Carpenter and R. Whitington , tr. H. T. Riley (1861) pp. 21--23, and A.B. Beaven, The Aldermen of the City of London (2008--13) II.xxviii.) In 1752 the start and end dates of the mayoral year were moved into early November (Beaven II.xxviii), where they have remained ever since, though with some changes in the specific dates and in the ceremonies. The shrieval year has consistently run from one 28 September to the next (see Liber Albus pp. 39--40 and Beaven II.xxxii).
This database places all mayors and sheriffs under the 12-month year (involving two calendar years) during which they served, even when they did not serve for all twelve months of that year. Some mayors and sheriffs have died, resigned, or been removed during their terms of office; this database provides death, resignation, or removal dates for them and specific start dates, wherever possible, for the mayors and sheriffs replacing them.
Until at least the mid-18th century, records show regular-term mayors swearing an oath of office at the Guildhall on the first inauguration day and on the second day another oath before the sovereign or his/her representatives at Westminster. Sometimes the second oath was sworn instead before the Constable of the Tower of London, as the monarch's representative. The sheriffs are recorded as being sworn at Guildhall, and fully assuming office, on 28 September; and until at least the mid-16th century (research on this matter has so far not been done past 1558) they also were presented subsequently, usually on 30 September, at Westminster (or the Tower). (For the sheriffs' presentation, see A. Lancashire, Civic London to 1558, Records of Early English Drama (2015) I.xxx-xxxi, xxxiv, 375--76, II.948, 773.) Replacement mayors usually also had a two-day installation, but sometimes the two installation days were compressed into one.
This database does not include, for regular-term mayors and sheriffs, their election dates (the established regular election dates varied considerably, over the years, and did not affect the regular start-of-term dates). Both election dates and installation dates are included, however, for replacement mayors and sheriffs, wherever available, as they provide the non-standard start-of-term dates for the replacements. For the replacement sheriffs, to 1558, these dates include any available for the Westminster/Tower presentation.