We usually say "six mois" = six months.
One half in French would be demi.
"une demi-soeur"
et demi
"I studied French last year."
in football a cntre half would be 'un milieu de terrain' in French.
"mi-trimestre"
demi-frère
"mi-trimestre"
un demi
Demi-journées
In French, you say the year 1822 as "mille huit cent vingt-deux."
In French, you would say "Il est quatre heures et demie."