Can I log metrics on two different time scales?

For example, I want to log training accuracy per batch and validation accuracy per epoch.

Yes, log indices like batch and epoch alongside your metrics. Use wandb.log({'train_accuracy': 0.9, 'batch': 200}) in one step and wandb.log({'val_accuracy': 0.8, 'epoch': 4}) in another. In the UI, set the desired value as the x-axis for each chart. To set a default x-axis for a specific index, use Run.define_metric(). For the example provided, use the following code:

wandb.init()

wandb.define_metric("batch")
wandb.define_metric("epoch")

wandb.define_metric("train_accuracy", step_metric="batch")
wandb.define_metric("val_accuracy", step_metric="epoch")