What does ddmmccyy mean?

Nothing!!!!

However, if you means Roman Numerals,, then the letters should be in CAPITALS .

'ddmmccyy' Should read 'DDMMCCXX'.

However more correctly it is ' MMDDCCXX'.

M = 1000

MM = 1000 + 2000 = 2000

D = 500

DD = 500 + 500 = 1000 = M ( again )

C = 100

CC = 100 + 100 = 200

X = 10

XX = 10 + 10 = 20

Hence 'MMDDCCXX' =

2000 + 1000 + 200 + 20 = 3,220 (= MMMCCXX'.