↩ 🔵 🔵 🔵 ❪✺ᵢ❫ Temporal Concepts ○ ❪✺₁❫ Metrological Classes ○ ❪✺₁❫ Physical Classes ○ Calendar ○꠹ Clock ○꠹ Date ○꠹ Day ○꠹ Timer ○꠹