First column:   year   month .   Number of months
Repeat day codes every columns.   Entry padding em.  

202520252025202520252025
JanFebMarAprMayJun
      
TuTu1Tu
We1We2We
Th2Th31Th
Fr3Fr42Fr
Sa411Sa53Sa
Su522Su641Su
      
Mo633Mo752Mo
Tu744Tu863Tu
We855We974We
Th966Th1085Th
Fr1077Fr1196Fr
Sa1188Sa12107Sa
Su1299Su13118Su
      
Mo131010Mo14129Mo
Tu141111Tu151310Tu
We151212We161411We
Th161313Th171512Th
Fr171414Fr181613Fr
Sa181515Sa191714Sa
Su191616Su201815Su
      
Mo201717Mo211916Mo
Tu211818Tu222017Tu
We221919We232118We
Th232020Th242219Th
Fr242121Fr252320Fr
Sa252222Sa262421Sa
Su262323Su272522Su
      
Mo272424Mo282623Mo
Tu282525Tu292724Tu
We292626We302825We
Th302727Th2926Th
Fr312828Fr3027Fr
Sa29Sa3128Sa
Su30Su29Su
      
Mo31Mo30Mo

35 rows

Notes on curious non-bug on my home machine:
with date_default_timezone_set('UTC') - be patient
without that declaration