Standard Tower Calendar

The Standard Tower Calendar is the common administrative reckoning by which floors, offices, and holdings of the Tower date their instruments, and the only calendar recognised for purposes of inter-floor correspondence. It comprises a fixed year of twelve months, eleven of which bear names and one of which does not; every month, including the unnamed one, contains precisely thirty Tower Standard Chronons. It is not to be confused with the Tower Calendar, the lunisolar system from which it derives and against which it is annually reconciled, nor with the Administrative Calendar, which is a schedule of deadlines rather than a sequence of days.

Adoption was not immediate and is still, in a narrow sense, contested. The reckoning was fixed during the Year of the Locked Shelf, when the Concordance Calendar was found to have drifted eight days against the stairwell chronometers of the lower hundreds, and the Librarian Calendar was in use in three scriptoria that have never fully abandoned it. The reconciliation is performed each month and recorded on the appropriate anticipatory entry, with corrections noted on the following day's volumetric sheet.

Structure of the year

The year runs to three hundred and sixty chronons. The eleven named months take their names from holdings rather than seasons — the Month of Dust is the second, and the months otherwise proceed by a sequence recorded in the Register of Month-Names (Scriptorium 9, folio 114). The twelfth month is designated the Unnamed Month and has never been assigned a name, though the omission has been proposed for correction in no fewer than nine Concordances and corrected in none.

The unnamed month is administratively the most demanding of the year, since instruments dated within it must carry the numeral of the month in place of a name, and the numeral is written in the older form. A clerk of the Ninth Registry, one Maret Ovin, filed a complaint in the winter of the Tower Year 14322 that she had spent eleven days of her allotted span disambiguating the twelfth-month numerals of instruments she had herself composed in the twelfth month of the preceding year. Her complaint was upheld, then overturned, then upheld again on the authority of two Concordances of opposing tenor; the numerals were left as they were.

The chronon and the question of the eighth

The chronon is a unit of the calendar and not of the clock. Clocks in the Tower run to their own reckoning, and the divergence between clock-time and chronon-time is handled by the Fiscal Epicycle, which absorbs the difference at the close of each accounting period rather than distributing it across the year. This arrangement produces the calendar's one genuine irregularity: the days numbered in an epicycle year are thirty per month without exception, but the events falling on them are occasionally out of order.

Whether the seven-day week survives the month of thirty is a matter of open scholarly dispute. Concordance 88, Annex 2, holds that the week is "a devotional convenience, not a measure," and therefore that four weeks and two days constitute a complete and lawful month. Concordance 91, Annex 2, ratified eight years later and by the same hand, calls the six-week month "the only defensible arrangement, the residue being distributed to the offices that most require it." The Office of Perpetual Affairs observes the first and cites the second when asked to justify its staffing rota. No instrument has ever been voided for using either.

"The calendar is not a description of time. It is an agreement about where to write things down. The agreement holds, and the time does what it likes."

— Third Concordance, preamble to the calendrical annexes

Observances and exclusions

The Standard Tower Calendar governs the placement of observances listed in the Standard Calendar of Observances, which is maintained under the same office and is, strictly speaking, a distinct instrument. The Day of Constant Hearth is fixed to the ninth chronon of the unnamed month; the Observance of the Locked Shelf falls on the first chronon of the second month. Omicron remnants survive in the dating of six observances, which is why the Omicron cycle must be consulted before any instrument touching the fire floors is sealed.

The calendar is expressly excluded from personal histories under the Bounded Recension, which forbids the use of administrative dating for anniversaries of persons. The Personal Registry of the Standard Calendar — not, despite its title, a register of persons — is exempt from standard archival decay protocols under Codicil 127, ratified 14 Thermidor, 1911, and is the only calendrical record permitted to be kept on vellum past the fourth recension.

Control of the standard

The authoritative copy is held at Standard Gauge, Floor 308, in a locked case measuring one cubit by two, checked against the sunless apertures at each equinox. Corrections are entered in red; corrections to corrections, in red over red. The case may be opened only in the presence of two Librarians, neither of whom may have signed the instrument under correction. Correction instruments are not to be carried up the stairwell between the third and the sixth landing, as the draft there has been known to lift loose vellum.

In practice most offices work from the Ascendant Calendar or from a hand-copied digest of the Spiral Calendar, and the standard copy is consulted chiefly when a discrepancy is large enough to be worth the walk.