@Siedlerchr 's solution will group the entries by year automatically if you create groups for each year or range of interest. It does not take long to create them, even if your library spans many years.
You can collect entries into the group by keyword or by expression. I recommend the expression option, because this is a faster way to create all the year-groups you need.
Collect by keyword
- Create a group
- Collect by
Searching for a keyword
- Field:
date
- Add criteria to
Keyword
- Select
Regular expression if applicable
Collect by expression
- Create a group
- Collect by:
Free search expression
- Add criteria to
Search expression
- Select
Regular expression if applicable
Field: date
Example: specific year
date=1975
Collects entries with date containing 1975. You would need to make a group like this for each year of interest. Copy the expression to your clipboard to paste into each new group, so you can modify only the last digit or two for most of the years.
Example: decade range (regular expression option)
date=197\d
Collects entries with a date between 1970 and 1979. Again, you would need to create groups for each range of interest (date=198\d, date=199\d, date=2000\d, and so on). You could nest subgroups of specific years under their respective decades.
I currently have a library containing bibtex and biblatex entries, some of which have a value for date, some for year, and a few for date and year. Searching in either one of these fields does not match data in the other, so in this scenario you need to convert all the entries to the same type or include the year and date fields in the filter.
Example: specific year in mixed bibtex/biblatex (regular expression option)
date=1975 or year=1975
Matches entries with a date or year containing 1975.
Creating the year-groups manually might be inconvenient, but compared to a manually adding entries to the group, it does have the advantage of staying up to date as the library grows. Also, if you have a recurring need to create groups for every year from 1950 to the present, you could do the task once in an empty library to use as a template. Copy the template library and important new entries each time you start a new library that you want to group by year.
Edit: corrected description of the last example.
