By default, the internal logs used to produce the licensing reports are only retained for 30 days. That is why you can't get information older than one month. I see two options. The first is change the retention period for _internal, restart Splunk, and wait a year for license data to accumulate. This will use a lot of storage. The other option is to create your own monthly license report and save it in a summary index that is kept for a year. Get your annual report from the summary index.
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