13*28

Quick comparison of calendars with 13 months of 28 days each
Calendar	Leap item	Leap position	Leap rule	Naming	Year start	1st day	Days without week	Days without month
28/293	day	flexible	294th day	numeric	Dec solstice	?	0	0
Abysmal	day	end	4:128	numeric	Dec solstice	Sat	1+	1+
13	day	end	4:100:400	numeric	Dec solstice	?	?	?
COIN	day	2nd month	4:100:400	numeric	Jan01	Mon	1+	0
Filianic	day	end	?	feminist	Mar equinox	Sun	0	0
Intl.	week	end	ISO	numeric	W01-1	Mon	0	0
Intl. Fixed	day	end	4:100:400	+ 07 “Sol”	Jan01	Sun	1+	1+
Jaktober	day	start	4:33	+ 13 “Jaktober”	Dec solstice	Mon	1+	1+
Kluznicki	day	end	astronomic	+ 07 “Aten”	Dec solstice	Mon	1+	0
Markels	day	end	?	zodiac	Sagittarius	Sun	1+	+
Modern Christian	day	end	4:33:293	Christian	?	Sun	1+	1+
Pax	week	almost end	%6 & 99 & 100:400	+ 12 “Columbus”	W01-1 – 1	Sun	0	(7)
Positivist	day	end	4:100:400	philosophic	1789-01-01	Mon	1+	0
Riparian	day	end	?	traditional + changes	Mar01	?	0	0
Sentinel	week	middle	6:50	lessons	Mar equinox	Sun	0	0
Sol	day	end	4:100:400	+ 07 “Sol”	Jan01	Sun	0	0
Nearest-Monday 13X28	week	end	Nearest Monday (arithmetical)	numeric, Esperanto	Dec solstice	Mon	0
Terran Comp.	day	end	4:128	numeric	Dec solstice	?	1+	1+
Leap-Month	month	flexible	294th month	numeric Esperanto	Jan	Mon	0	0
Todd’s	day	end	?	zodiac	?	?	?	1+

Quick comparison of month names, starts and lengths
Calendar	M01			M02			M03			M04			M05			M06			M07			M08			M09			M10			M11			M12			M13
		001	28		029	28		057	28		085	28		113	28		141	28		169	28		197	28		225	28		253	28		281	28		309	28		337	28+
		W01-1	28		W05-1	28		W09-1	28		W13-1	28		W17-1	28		W21-1	28		W25-1	28		W29-1	28		W33-1	28		W37-1	28		W41-1	28		W45-1	28		W49-1	28
COIN/Super/PINC	01 Anu	001	28	02 Beo	029	29+	03 Cip	058+	28	04 Deq	086+	28	05 Ero	114+	28	06 Fis	142+	28	07 Gat	170+	28	08 Hup	198+	28	09 Ivo	226+	28	10 Jaw	254+	28	11 Kix	282+	28	12 Lay	310+	28	13 Mez	338+	28
Filianic	11 Herthë	~361	28	12 Brighë	~024	28	13 Moura	~052	28+	01 Culverine	~080	28	02 Maia	~108	28	03 Hera	~136	28	04 Rosëa	~164	28	05 Kerëa	~192	28	06 Vaskaras	~220	28	07 Abolan	~248	28	08 Vois	~276	28	09 Werdë	~304	28	10 Astraea	~332	28
Intl.	M01	W01-1	28	M02	W05-1	28	M03	W09-1	28	M04	W13-1	28	M05	W17-1	28	M06	W21-1	28	M07	W25-1	28	M08	W29-1	28	M09	W33-1	28	M10	W37-1	28	M11	W41-1	28	M12	W45-1	28	M13	W49-1	28+
Intl. Fixed	01 January	001	28	02 February	029	28	03 March	057	28	04 April	085	28	05 May	113	28	06 June	141	28+	07 Sol	169+	28	08 July	197+	28	09 August	225+	28	10 September	253+	28	11 October	281+	28	12 November	309+	28	13 December	337+	29
Jaktober	01 January	~355	28	02 February	~018	28	03 March	~046	28	04 April	~074	28	05 May	~102	28	06 June	~130	28	07 July	~158	28	08 August	~186	28	09 September	~214	28	10 October	~242	28	11 November	~270	28	12 December	~298	28	13 Jaktober	~326	29+
Kluznicki	01 January	~355	28	02 February	~018	28	03 March	~046	28	04 April	~074	28	05 May	~102	28	06 June	~130	28	07 Aten	~158	28	08 July	~186	28	09 August	~214	28	10 September	~242	28	11 October	~270	28	12 November	~298	28	13 December	~326	29+
Markels	01 Sagittarius	~352	28	02 Capricornus	~015	28	03 Aquarius	~043	28	04 Pisces	~071	28	05 Aries	~099	28	06 Taurus	~127	28	07 Gemini	~155	28	08 Cancer	~183	28	09 Leo	~211	28	10 Virgo	~239	28	11 Libra	~267	28	12 Scorpio	~295	28	13 Ophiucus	~323	29+
Modern Christian	01 Pete	W52/3-7	28	02 Drew	W04-7	28	03 Jim	W08-7	28	04 Han	W12-7	28	05 Phil	W16-7	28	06 Bart	W20-7	28	07 Tom	W24-7	28	08 Levi	W28-7	28	09 Jake	W32-7	28	10 Thad	W36-7	28	11 Sim	W40-7	28	12 Jude	W44-7	28	13 Josh	W48-7	28+
Pax	01 January	W01-1	28	02 February	W05-1	28	03 March	W09-1	28	04 April	W13-1	28	05 May	W17-1	28	06 June	W21-1	28	07 July	W25-1	28	08 August	W29-1	28	09 September	W33-1	28	10 October	W37-1	28	11 November	W41-1	28	12 Columbus	W45-1	28+	13 December	W49/50-1	28
Positivist	01 Moses	001	28	02 Homer	029	28	03 Aristotle	057	28	04 Archimedes	085	28	05 Caesar	113	28	06 Saint Paul	141	28	07 Charlemagne	169	28	08 Dante	197	28	09 Gutenberg	225	28	10 Shakespeare	253	28	11 Descartes	281	28	12 Frederic	309	28	13 Bichat	337	28+
Riparian	12 February	003	28	13 Ultimus	031	28	01 Ryo	059	28	02 April	087	28	03 May	115	28	04 June	143	28	05 Quintil	171	28	06 Sextil	199	28	07 September	227	28	08 October	255	28	09 November	283	28	10 December	311	28	11 Undecimber	339	29+
Sentinel	11 Gyan	~361	28	12 Gabriel	~024	28	13 Eden	~052	28	01 Tomas	~080	28	02 Hugh	~108	28	03 Ashia	~136	28	04 Arabela	~164	28	05 Amadea	~192	28	06 Jomei	~220	28	07 Sophia	~248	28+	08 Cheyenne	~276	28	09 Olivia	~304	28	10 Cosmos	~332	28
Sol	01 January	001	28	02 February	029	28	03 March	057	28	04 April	085	28	05 May	113	28	06 June	141	28	07 Sol	169	28	08 July	197	28	09 August	225	28	10 September	253	28	11 October	281	28	12 November	309	28	13 December	337	29+
Nearest-Monday 13X28	01 Unua	W52-1	28	02 Dua	W04-1	28	03 Tria	W08-1	28	04 Kvara	W12-1	28	05 Kvina	W16-1	28	06 Sesa	W20-1	28	07 Sepa	W24-1	28	08 Oka	W28-1	28	09 Nua	W32-1	28	10 Deka	W36-1	28	11 Dekunua	W40-1	28	12 Dekdua	W44-1	28	13 Dektria	W48-1	28+
Gorman	01 March	001	28	02 April	029	28	03 May	057	28	04 June	085	28	05 Quintilis	113	28	06 Sextilis	141	28	07 September	169	28	08 October	197	28	09 November	225	28	10 December	253	28	11 January	281	28	12 February	309	28	13 Gormanuary	337	28+
New Earth	01 January	W01-1	28	02 February	W05-1	28	03 March	W09-1	28	04 April	W13-1	28	05 May	W17-1	28	06 June	W21-1	28	07 Luna	W25-1	28	08 July	W29-1	28	09 August	W33-1	28	10 September	W37-1	28	11 October	W41-1	28	12 November	W45-1	28	13 December	W49-1	28+