The histogram below shows the total return of long-dated treasuries over a rolling 4-month period since 2007. The rationale for using a 4-month period is that the climb in long-term rates started 4 months ago (a 3-month period produces a very similar result.) The leftmost bucket contains five periods that constitute the worst treasury losses since 2007. All five of these periods ended within the past 10 days, indicating that the recent losses are the worst in at least 6 years.
For those who have access to this index on a total-return basis going back further that 2007, it would be interesting to see how far back one actually has to look to find an equivalent correction to bond prices.