Merci Marc, pour cette excellente question:
Just one question about a pronunciation :
It seems that September must be pronounced with the voyel “e” as the French “é” though December is pronounced with the voyel “e” as the French “i” .
Could you tell me the reason why ?
The French vowel ‘i’ is between the English sounds ‘ee’ like ‘sheep’ and the ‘I’ like ‘ship’. The stressed syllable in both ‘September’ and ‘December’ is in the middle, ‘sepTEMber’, ‘deCEMber’. The difference is the fact that there are two consonants after the ‘e’ in September, but only one after the ‘e’ in December. The ‘e’ in December, because it is not stressed becomes contracted like the French ‘i’. We can hear the same in the word ‘develop’. French speakers often mispronounce this word, putting the accent on the first syllable when in fact it should be pronounced ‘diVELop’ (sorry I can’t use the correct phonetic characters on a web page).
This can be compared to the way the letter ‘e’ changes in French depending on whether there is one or two consonants after it. Think about the ‘e’ in Renault (one consonant) and Rennes (two consonants).
I hope this answers your question. Try to focus more on the sounds and practise saying them more than trying to find out why! Often the best answer is ‘c’est comme ça’!