Third declension neuter nouns in the nominative singular and the accusative singular are unpredictable. That’s why you’ll see a dash in the endings for the nominative and accusative.

N: –

G : –is

D : –ī

Acc :  –

Abl : –e

The endings for the Latin word for foot:

N : pēs

G : pedis

D : pedĪ

Acc : pedem

Abl : pede

The endings for the Latin word for time:

N : tempus

G : temporis

D : temporĪ

Acc : tempus

Abl : tempore