Pillar printing for era_year

[Joe Roe]

[Joe Roe]

Before:

tibble(era = era(c("cal BP", "BC", "AH")), unit = era_unit(era))
# A tibble: 3 × 2
                                                                                             era                                 unit
                                                                                           <era>                           <era_year>
1          Before Present (cal BP): Gregorian years (365.2425 days), counted backwards from 1950      Gregorian years (365.2425 days)
2                  Before Christ (BC): Gregorian years (365.2425 days), counted backwards from 1      Gregorian years (365.2425 days)
3 Anno Hegirae (AH): Islamic lunar years (354.36708 days), counted forwards from 622.53662977337 Islamic lunar years (354.36708 days)

After:

# A tibble: 3 × 2
     era          unit
   <era>    <era_year>
1 cal BP     Gregorian
2     BC     Gregorian
3     AH Islamic lunar