From the “Iranian festivals” package

Great Chelleh

The forty coldest days of winter, from 1 Dey to 10 Bahman

Historical confidence: Attested

In nearby years

1403 Saturday 1 Dey 1403 21 December 2024 40 days
1404 Monday 1 Dey 1404 22 December 2025 40 days
1405 Tuesday 1 Dey 1405 22 December 2026 40 days
1406 Wednesday 1 Dey 1406 22 December 2027 40 days
1407 Thursday 1 Dey 1407 21 December 2028 40 days