40 is a significant number in Jewish-Christian scripture:
In Genesis, the flood which destroyed the earth was brought about by 40 days and nights of rain.
The Hebrews spent 40 years in the wilderness before reaching the land promised to them by God.
Moses fasted for 40 days before receiving the ten commandments on Mount Sinai.
Jesus spent 40 days fasting in the wilderness in preparation for his ministry.
Most Christians regard Jesus' time in the wilderness as the key event for the duration of Lent.
Lent is an old English word meaning 'lengthen'. Lent is observed in spring, when the days begin to get longer.
Purple is the symbolic colour used in some churches throughout Lent, for drapes and altar frontals.
Purple is used for two reasons: firstly because it is associated with mourning and so anticipates the pain and suffering of the crucifixion, and secondly because purple is the colour associated with royalty, and celebrates Christ's resurrection and sovereignty.