Correct spelling, explanation: many words in English come from other languages. It is no different in the case of the word December, which comes from Old French and Latin. If you want to know how to spell it correctly, just look at the etymology. We can see three of the same vowels in this noun. It would be a mistake to think that the first -e should be replaced with an -i. Dicember is not correct.

Definition of December:
noun, the twelfth and final month of the Gregorian calendar, has 31 days
The December air was cold and crisp, and the snowflakes fell gently to the ground.
We usually exchange gifts with our family and friends in December to celebrate the holiday season.

Collocations with December:
Some most commonly used collocations include: December sales, December decorations, December blues, December chill
Retailers often offer deep discounts during December sales to encourage shoppers to buy holiday gifts.
Many people enjoy putting up festive December decorations like wreaths, lights, and ornaments.
For some people, the dark, cold days of December can trigger feelings of sadness or depression, known as the December blues.
As the temperature drops, many people enjoy cozying up with a warm blanket and some hot cocoa to beat the December chill.

Incorrect spelling, explanation: when spelling the word December, we should look at its etymology. It is a borrowing from Middle English December, as well as from Latin december. There is only one vowel in this word: -e. There is no place for the letter -i here. That’s why Dicember is just a mistake. This spelling would also change the pronunciation.

Incorrect spelling

Incorrect spelling