"Dancing at Whitsun" has similar problems. It was written in the 1960s to commemorate the deaths in WW1 of almost the entire male population of a Sussex village.

The central character is the widow of one of the fallen, and "fifty long springtimes since she was a bride" indicated that the lady in question was then in her 70s. In 2003, changing the lyric to "ninety long springtimes" would make her well over 100!

This song doesn't really lend itself to being updated, so I nowadays revert to the original "fifty" and preface it with a brief introduction. It would be a shame were it not to be sung because of the passage of time.

"They shall not grow old, as we that are left grow old
Age shall not weary them, nor the years condemn
At the going down of the sun and in the morning
We will remember them."
(For the Fallen - Lawrence Binyon)

Alan