epoch value in ModelCheckpoint is inconsistent

[SKb10]

Hi:
Keras offer a easy way to add epoch to the model name when saving
https://github.com/fchollet/keras/blob/master/keras/callbacks.py#L400
filepath = self.filepath.format(epoch=epoch, **logs)

But with the code like below one, which is suppose to save model every 20 eopch:

checkpointer = ModelCheckpoint(filepath="{epoch:03d}"+".hdf5", period=20)

It save the model every 20 epochs like:
019.hdf5
039.hdf5

The model saving operation does happen after 20, 40 epoch were finished.
Is there a bug, or I missed something(?

thanks for your review

[rravu3]

Don't think it's a bug. The epoch value coming into the callback is zero indexed.

[stale]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed after 30 days if no further activity occurs, but feel free to re-open a closed issue if needed.

[ozabluda]

fixed in #8137