When did adding candles to a birthday cake originate?

The 15th century ... I think

Cultures have been creating celebratory ‘cakes’ (the term cake and bread were often interchangeable) for thousands of years. However, cakes, specifically for birthdays, similar to what we enjoy today, are believed to have originated in Germany in the 1400’s. Before that time, cakes were almost solely for the celebration of weddings but bakeries began to market them for birthdays as well.

As with the marketing of birthday cakes, the addition of candles is also attributed to the Germans around the 1700’s when Kinderfesten, birthday celebrations for children, became more common. The custom was to place a candle for each year of their life as well as extra candles to represent years to come.