I had a couple of places where I needed to display billing periods with date formatting and a custom separator. Here is a field formatter that lets you select the date format for your dates, whether to display or hide the start date or end date, the separator between start and end dates if they're both displayed.
Needs review
1.0
Code
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It's likely this issue predates Contrib.social: some issue and comment data are missing.
Please ignore patch no. 14, it's incomplete.
Re-rolling #4 for commerce_recurring 1.0-rc1