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

202620262026202620262026
JanFebMarAprMayJun
      
WeWe1We
Th1Th2Th
Fr2Fr31Fr
Sa3Sa42Sa
Su411Su53Su
      
Mo522Mo641Mo
Tu633Tu752Tu
We744We863We
Th855Th974Th
Fr966Fr1085Fr
Sa1077Sa1196Sa
Su1188Su12107Su
      
Mo1299Mo13118Mo
Tu131010Tu14129Tu
We141111We151310We
Th151212Th161411Th
Fr161313Fr171512Fr
Sa171414Sa181613Sa
Su181515Su191714Su
      
Mo191616Mo201815Mo
Tu201717Tu211916Tu
We211818We222017We
Th221919Th232118Th
Fr232020Fr242219Fr
Sa242121Sa252320Sa
Su252222Su262421Su
      
Mo262323Mo272522Mo
Tu272424Tu282623Tu
We282525We292724We
Th292626Th302825Th
Fr302727Fr2926Fr
Sa312828Sa3027Sa
Su29Su3128Su
      
Mo30Mo29Mo
Tu31Tu30Tu

35 rows

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