The general answer to this is, when they beginning to get tired and before they’re crying.

Learn and look for their tired cues, these are the sounds and signs your baby makes as it begins to get tired. I have found Tracy Hogg's advice to put baby to bed on the third yawn, and certainly by the '3 mile stare', has helped many parents.

Studies suggest that 90% of babies presenting with 'colic' are in fact overtired rather than suffering with gastric problems. So if you have a baby with colic its worth really making a study of their tired cues and getting them ready for sleep well in advance of the grumpy stages of tiredness.

Tired cues:

• turning head away

• quickly losing interest in things

• three mile stare (that open eyed, staring in the distance without blinking)

• yawning, faster

• more frenetic limb movements

• grumbling noises, sometimes high pitched noises

• arching

• rubbing eyes

• yanking ears

• burying face in your shoulder

What's a good bedtime?

Curiously, the sleep experts seems to agree that early evening is the right time to put a baby to bed ie, between 6.30 and 7.30 pm.

Experts also agree that a consistent bedtime is important, particularly if you are trying to train your baby to sleep better.

For more information and help learning cues

The Baby Whisperer by Tracy Hogg is an excellent book

The social baby: Understanding Communication from Birth. by Lynne Murray and Liz Andrews should be standard issue to all new parents. It’s a photostory book showing how babies signal what they’re feeling.