How to predict the probability of an event?
Please double-check if there's the only data you have got, because all you have is a single predictor date.

If this is indeed your only data source, then you only have a single predictor, and your independent variable is continuous. Now, you should plot date vs amount and fit a single linear regression. Does the fitting look good? Only you can tell because we don't have the full data-set.

If it's not a good fit, look at the plot and ask yourself does this look like a curve? If so, you might want to fit a spline curve or something like that.

You should also check the autocorrelation. This makes sense because your data look like a time series (you'll need to check it yourself). If this is the case, you might want to consider MA and ARCH model.

It's not possible for us to give you accurate advice because we don't know your data.