First teeth at 9 months. Babies saliva glands start working from about 3 months and parents often mistake this for teething. We thought ours were "teething" from about 12 weeks but it took months for any teeth to actually appear.
First tooth appeared on his birthday, 9 months corrected age. 3 others followed within a week. But we thought he was 'teething' from at least 4 months of age: dribbling, chewing with increasing urgency, sore gums etc. I think there is a lot of stopping and starting going on with teeth before they eventually break through.
13 months actual age before any appeared... and then five did in one go (poor kid!) Think she's just a natural late teether anyway though - her 2 year ones are taking their sweet time appearing as well.