Solved the problem (kludgily) on my own; for posterity:
1. By logging on to iCloud.com and trying to add a calendar event to be sync’d, I got an error message stating that I had exceeded my 25,000 event limit. (I have so many because I have been using Calendar as a diary from the early 2000’s.) For a company that issues user-interface guidelines to its developers, it’s ironic that neither OS-X or iOS gave me any warning or explanation for the sync failure. I deleted some calendars that were more than 10 years old, and sync started working.
2. I manually retrieved and re-entered the recently-added events by using terminal commands. The following commands will list events that were added in February 2016:
cd /Volumes/Big4Tv/Archive/Calendars\ and\ Reminders\ 2.9.16,\ 10.52\ AM.icbu
find . -name ‘*.ics' -exec grep -q CREATED:201602 {} \; -print -exec cat {} \;
Explanation:
The path following "cd" above is the archive; no need to type it, just drag and drop from a Finder window.
" find . -name '*.ics' " searches the archive (which is a package) for files with ics suffixes -- there are one file per calendar event
" -exec grep -q CREATED:201602 {} \; " runs the grep command to look for text that indicates the event was created in Feb 2016
" -print " if the grep command succeeds, print the name of the ics file.
" -exec cat {} \; " and then display the text inside the file, which will look something like this:
./Calendars/38D7571D-5956-4D4A-8152-7E48400A85DE.caldav/65A23878-CB41-47A4-90BA- 0C883D09A2BC.calendar/Events/178435BA-A2D8-4C60-9F19-2A48F0020406.ics
BEGIN:VCALENDAR
VERSION:2.0
PRODID:-//Apple Inc.//Mac OS X 10.11.2//EN
CALSCALE:GREGORIAN
BEGIN:VEVENT
TRANSP:OPAQUE
DTEND;TZID=America/Los_Angeles:20160202T123000
UID:178435BA-A2D8-4C60-9F19-2A48E0020406
DTSTAMP:20160202T203219Z
X-APPLE-SCHEDULETAG:
X-APPLE-SERVERFILENAME:178435BA-A2D8-4C60-9F19-2A48F0020406.ics
SEQUENCE:0
X-APPLE-EWS-BUSYSTATUS:BUSY
SUMMARY:Call Peg\, email
DTSTART;TZID=America/Los_Angeles:20160202T110000
X-APPLE-TRAVEL-ADVISORY-BEHAVIOR:AUTOMATIC
CREATED:20160202T203209Z
X-APPLE-ETAG:"C=38048@U=048b109f-f9b8-4483-b2fa-47ed7334f6f0"
END:VEVENT
END:VCALENDAR
A more compact output can be gotten using a longer “find” command, which prints the events summary, start and end times:
find . -name ‘*.ics' -exec grep -q CREATED:201602 {} \; -print -exec grep -h SUMMARY {} \; -exec grep -h DTSTART {} \; -exec grep -h DTEND {} \;
./Calendars/38D7571D-5956-4D4A-8152-7E48400A85DF.caldav/65A23878-CB41-47A4-90BA- 0C883D09A2BB.calendar/Events/178435BA-A2D8-4C60-9F19-2A48E0020406.ics
SUMMARY:Call Peg\, email
DTSTART;TZID=America/Los_Angeles:20160202T110000
DTEND;TZID=America/Los_Angeles:20160202T123000
