Calendar Wiki

Cal7 is a proposed leap week calendar that heavily relies on the number seven. A week has, as usual, 7 days, but also a month has 7 weeks and a year has 7 months. The only deviation are odd-numbered months, which have 8 weeks, except for the last one where the eighth week is the leap week. A leap week occurs every 7th year and every 29th year (the rest of the leap rule is yet to be defined). Cal7 can thus be considered a loose solar calendar.

The ISO 8601-like date format is ±CCYY-M-W-D. If not specified otherwise, Cal7 agrees with this international standard, e.g. that Monday is the first day of the week.

English names
Ordinal Day Week Month
1 Monday Monweek Monmonth*
2 Tuesday Tuesweek Tuesmonth
3 Wednesday Wednesweek Wednesmonth*
4 Thursday Thursweek Thursmonth
5 Friday Friweek Frimonth*
6 Saturday Saturweek Saturmonth
7 Sunday Sunweek Sunmonth†
8 (Holiweek)

In the table, an asterisk * denotes months that always include Holiweek and a dagger † shows the month that is 8 weeks long only in leap years.


The following table compares Cal7 with similar proposals, assuming weeks start on Monday in all cases. The academic terms listed are synchronized with Cal7 months; they could be aligned with other months instead.

Relation to other leap week calendars
Week 01 02 03 04 05 06 07 08 09 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53
13mon Janon Febron Marchon Apron Mayon Junion Extron Julon Augon Septon Octon Novon Decon †
5:4:4 Janaire Febraire Marchose Aprilose Mayose Junal Julial Augial Septidor Octidor Novidor Decaire †
4:5:4 Janose Febrose Aprial Mayal Julidor Augidor Octaire Novaire
4:4:5 Febral Marchal Maydor Junidor Augaire Septaire Novose Decose †
Quarter quart 1 quart 2 quart 3 quart 4
7:6 Bol Sar Tan Lit Nas Mon Sam Yul †
4:5* Janose Febrose Marchose Aprilose Mayose Junal Julidor Augidor Septidor Octidor Novidor Decaire †
9:9:8 sester 1 sester 2 sester 3 sester 4 sester 5 sester 6
5:5:6:5 Primoth Secoth Tertoth Quaroth Quintoth Sixtoth Septoth Octoth Novoth Decoth †
10:11 quinter 1 quinter 2 quinter 3 quinter 4 quinter 5
8:7 Monmonth Tuesmonth Wednesmonth Thursmonth Frimonth Saturmonth Sunmonth †
 Terms Spring semester Summer break Fall semester
Winter semester Spring break Summer semester Fall break Winter semester
Epiphany/Hilary trimester Trinity trimester Summer break Michaelmas trimester


The Christian holidays are fixed as follows: Carnival, Easter and Pentecost are at month boundaries, 7 weeks apart. Christmas Eve is one week before New Year’s Eve unless there’s a leap week and Lady Day is 40 weeks before Christmas (not 9 months).

Note that Halloween is on -6-6-6, a Saturday. Most holidays are conveniently placed onto Sundays, unless they are already associated with a fixed day of the week.

Fixed (Christian) holidays
Holiday Date Notes
New Year -1-1-1 the first day of Monmonth
Circumcision of Christ -1-1-1 the first day of Monmonth
Epiphany -1-1-7 was 6 Jan or Sunday close by, also Theophany
Candlemas -1-4-7 was 2 Feb or Sunday close to it, Presentation of Jesus at the Temple
Valentine’s Day -1-6-7 was 14 Feb
Shrove Monday -2-1-1 the first day of Tuesmonth, 7 weeks before Easter Carnival
Mardi Gras -2-1-2
Ash Wednesday -2-1-3
Women’s Day -2-2-7 was 8 Mar
Lady Day -2-3-7 was 25 Mar, Feast of the Annunciation of the Blessed Virgin
Maundy Thursday -2-7-4 Easter
Good Friday -2-7-5
Easter Sunday -2-7-7 the last day of Tuesmonth (a week later than proposed for Sym454)
Easter Monday -3-1-1 the first day of Wednesmonth
Labor Day -3-3-3 -3-3-1? -3-7-5?, Workers’ Day was 1 May (or 1st Mon in Sep in NA)
Mother’s Day -3-3-7 was 2nd Sun in May etc.pp.
Father’s Day -3-4-7 was 3rd Sun in Jun etc.pp.
Ascension -3-7-4 40 days after Easter Pentecost
Pentecost Sunday -3-8-7 the last day of Wednesmonth, 7 weeks after Easter
Pentecost Monday -4-1-1 the first day of Thursmonth, Our Lady of Holy Church
Trinity Sunday -4-1-7
Corpus Christi -4-2-4 60 days after Easter
Midsummer -4-2-7 was ca. 21 Jun
Feast of the Transfiguration -4-7-7 the last day of Thursmonth, was 6 Aug
Feast of the Cross -5-8-7 the last day of Frimonth, was 14 Sep
Michaelmas -6-1-7 was 29 Sep, Feast of the Archangels
Halloween -6-6-6 a Saturday, was 31 Oct, Samhain All Hallows
All Hallows -6-6-7 was 1 Nov
All Saints -6-7-7 the last day of Saturmonth
Thanksgiving -7-1-7 Harvest feast, was 4th Thu in Nov, 2nd Mon in Oct, 1st Sun in Oct etc.pp.
1st Advent Sunday -7-2-7 Advent
St. Nicklas -7-3-6 was 6 Dec
2nd Advent Sunday -7-3-7
3rd Advent Sunday -7-4-7
4th Advent Sunday -7-5-7
Christmas Eve -7-6-6 Christmas
Christmas Day -7-6-7 was 25 Dec
Boxing Day -7-7-1 was 26 Dec
New Year’s Eve -7-7/8-7 depends on leap week

See also[]