Excel's date functions manipulate dates stored as serial numbers. AUJOURDHUI (TODAY) gives today's date, ANNEE (YEAR), MOIS (MONTH) and JOUR (DAY) extract elements, DATE assembles a date, DATEDIF and JOURS (DAYS) calculate gaps, MOIS.DECALER (EDATE) and FIN.MOIS (EOMONTH) move a date. A date entered as text must first be converted.
Example
=DATE(ANNEE(A2);MOIS(A2)+1;1) // first day of the next month