Hours, Minutes, Seconds:

Day is divided into 10 hours
Each hour is divided into 100 minutes
Each minute is divided into 100 seconds
Therefore 1 french second = 60*60*24/100*100*10 = 0.864 regular seconds
 

Years, Months, Days:

Year is divided into 12 months
Each month is divided into 3 decades of 10 days each
The 12 months are followed by 5 additional days (6 additional days in leap year)
Leap years occur in year 3, 7, 11, 15, 20, and thereafter every year divisible by 4
   except if year is divisble by 100, then it must also be divisible by 400 to be a leap year

Names of months:

1. Vendémiaire
2. Brumaire
3. Frimaire
4. Nivôse
5. Pluviôse
6. Ventôse
7. Germinal
8. Floréal
9. Prairial
10. Messidor
11. Thermidor
12. Fructidor

Names of the additional days:

1. Fete de la vertu (Celebration of virtue)
2. Fete du genie (Celebration of genius)
3. Fete du travail (Celebration of labor)
4. Fete de l'opinion (Celebration of opinion)
5. Fete des recompenses (Celebration of rewards)
6. Jour de la revolution (Day of the revolution) (the leap day )

The names of the days in each decade are:

1. Primidi
2. Duodi
3. Tridi
4. Quartidi
5. Quintidi
6. Sextidi
7. Septidi
8. Octidi
9. Nonidi
10. Decadi
 

Origin

1 Vendémiaire in year 1 =  September 22, 1792