Are these calendars you have write permission for, i.e. are you allowed to add events?

No, except for one, my google calendar which is empty as I don't use it. The rest are are weather, holiday and various sports calendars associated with google. These generally update once a day to remove yesterday's weather and add a day three days from today and to add yesterday's final scores. Obviously the holiday calendar generally has no changes.

Try to set those calendars you don't write to to read-only.

Right-click the calendar in the left pane - Properties

Also adjust the 'Refresh' interval. E.g. for the 'Holiday' calendar it can be set to 'never'. You can manually trigger calendar synchronization at any time if needed.

I'm sorry, when I replied to, "Are these calendars you have write permission for, i.e. are you allowed to add events?", I assumed that meant are they read-only. With this new understanding, all of the calendars with the exception of my google calendar are read-only. 'Never' is not an option for refresh, however, 'manually' is an option. Currently they are all set to the longest automatic refresh of 60 minutes. I'm sure I can set them all to manually refresh and trigger that event every morning myself. I can try that and restart Thunderbird to see it's effect.

'Never' is not an option for refresh, however, 'manually' is an option.

Yes, 'manually' is what I meant.

I changed the refresh option to manually for all calendars and restarted Thunderbird. The calendars automatically refresh on start up. The problem still existed. I shut down and rebooted just in case there was a remnant held in memory and restarted Thunderbird. The problem still exists.

Have you logged in to Google and checked that everything is OK in your calendar there? I'm wondering if maybe one of the 'add in' calendars isn't updating properly and that's causing everything to stall.

I double checked google calendar just to be safe in case I missed something and everything seems fine. All calendars properly populated. Thanks for the idea.

UPDATE: When I first started Thunderbird this morning, @ 8:16a EDT, the calendars synced and did not hang up. However, for whatever reason, @ 8:42a EDT the calendars tried to automatically sync, even though they are set to manually sync, and have hung up as per my original post.

I suppose all those calendars are network calendars, correct?

If so, try to delete them, one at a time. Restart Thunderbird. Re-create the previously deleted calendar. Check whether it would still hang upon synchronizing.

Sorry for the delay in responding. Yes, all the calendars are network calendars. I tried your suggestion and removed the first calendar in the list to hang up. I did not re-create it yet. I restarted Thunderbird and the remaining calendars synchronized at startup but did not hang up. After an hour and a half they did not try to synchronize automatically. I manually synchronized them with no hang up. I will now try to re-create the calendar I removed to see if it will cause a hang up again. If so, I know to remove it. I will leave this question open for another day just to see if the problem returns. Thanks for all the help.

After performing an update to my anti-malware software I needed to reboot and when Thunderbird restarted I immediately had two calendars hang up. I will try to remove the calendars one at a time tomorrow to see if I can figure out which calendar(s) might be a problem.

Are these all Google calendars? Is the Google birthdays calendar included? Are you using the gdata provider or caldav? (Very important) What anti virus/malware product?

Caldav operates on the same ports as web pages, so your anti virus might be treating it like some suspicious web activity from an email client.

When I started Thunderbird this morning no calendar hung up. I manually synchronized twice to see if a calendar would hang up and none did. This is part of the problem, it can be random and then go through a period of time when it happens regularly.

Yes they are all google calendars. I am not using the birthdays calendar. I have a separate local calendar for birthdays. I am using the GData Provider For Google Calendar 2.7. The malware product which updated is Hitman Pro 3.7. I also have Norton Security Suite 22.6.0.142 and Malwarebytes 2.3.125.0. No security product has given any alert that a file or process is questionable and they have with other software which I was able to whitelist.

Another possible important point. This morning I needed to fill in each of my passwords manually. I usually enter it in the first box and copy and paste it into each of the following boxes. It requests a password for each email account and calendar. It wouldn't allow me to copy and paste this morning. I use a master password which I thought would allow me to only enter it once. I don't remember having to enter each password manually in the past. I don't believe this is an issue since all the email accounts download new emails and calendars have worked properly on occasions when I copied and pasted but I am not the expert.

My first suggestion would be drop the gdata provider in favor of caldav. It is basically simpler and removes another layer of abstraction (gdata provider). You just need to locate the calendar URL in Google.

I wrote a bit on the topic a year or so ago. See http://thunderbirdtweaks.blogspot.com.au/2014/10/lightning-and-caldav.html

Thanks for the suggestion. I will follow up on the article and implementation after I return from an appointment. Once done I will post a follow up.

THANKS TO EVERYONE WHO HAS TAKEN THE TIME TO TRY TO HELP ME!

I attempted to use the caldav version of the calendars and ran into an issue. It requires the use of cookies to work. I don't have cookies enables as I have read of possible security issues. I also prefer not to be tracked for advertising and purchasing records. I am open to opinions on this.

When I restarted Thunderbird after returning from my appointment I had calendars hang up. I removed one of the calendars and restarted Thunderbird with no hang up. So far anytime I remove any calendar and restart it restarts with no hang ups. They eventually return. Is caldav the solution or are there other possibilities?

Cookies are a part of the 21st century web. Disabling them is really going to hurt you more in the long term than save you.

Nortons for 20 years or more have crowed about how they are saving you by doing something with your cookies, this has lead to a view that cookies are bad. Cookies are no more bad than guns or cars. They are not an issue unless misused.

Sure cookies can be used to track you, that is their purpose. In the case of caldav it is to place a file on your computer to manage ongoing security while your session is active. So the server remembers who you are.

Likewise on the wen I really like the fact that my ebay account is permanently signed it to clicking buy it now does not start some password process.

If you are concerned about privacy, have a look on just about every web page you visit. See those littler Facebook and Twitter images.

Things like this

They do a far better job of tracking you and your families actions on the internet that any cookie will ever manage. Has your browser ever been on a porn site? One supporting a radical idea or a socially volatile one like gay marriage. Twitter and Facebook know about it. No cookies involved. and despite any of the fancy do not track stuff Mozilla have come up with.

Just as this site reports that you came here using windows 7 64bit on a Firefox 45 browser, it was also informed of your ip address (It had to reply) Facebook and twitter and others can capture such information for every page you visit with their logo on it. Your privacy is really already toast.

This is a good discussion on cookies, what they are and the risks. http://resources.infosecinstitute.com/risk-associated-cookies/

If you have never heard of the risks they list (most are new to me), there is a reason for that. They are hacks designed for identity theft and corporate espionage. not general web browsing or email. Of more importance to your personal security is that all web addresses start with HTTPS: not HTTP:

In the case of Google, they are in the process of moving all things password to the oAuth2.0 specification, or their implementation of it. That specification requires that a token be stored on the local machine. While I make no claims to be a security expert, I would guess that the cookie blocking flags also block oAuth2.0 tokens. In short, there will come a time that your either have tokens allowed or you do not use Google except in a web browser.

Matt, Thank You so much for taking the time to cover an off topic issue in such depth for me. My fear has always been someone physically stealing my laptop would have easier access to accounts from stored user names (and maybe passwords) leading to them only having to learn passwords. Maybe I am a bit overly concerned especially since I use sign on security of either a password or fingerprint even if from hibernation or sleep. I have always liked the convenience provided when I did use cookies. I will certainly read the article you mentioned and rethink my position. I wish I had all day to dedicate to this so I can resolve it quickly and not keep you waiting so long for responses. I really appreciate all you are doing to help me resolve this, and other, issues. I must say that I am certainly learning. You really can teach an old dog new tricks! Thanks again and I will respond as soon as possible.