It's probably too late to tender your shares, unless the offer is extended. If your shares are in a brokerage account, they are not literally in your name, but instead they're in the broker's name (what they call the street name), with your name registered as the beneficial shareholder. When you tell your broker you'd like to tender your shares, they have to physically complete the paperwork, and have it delivered to the transfer agent before the deadline. That takes time, obviously. Each broker will have set a final notice deadline to guarantee that the tendering process will be completed on your behalf, but that's an internal decision that might be different for different investors. Some brokers will accept late tenders, but on the condition that they will be completed on a "best efforts" basis, i.e. with no guarantee.
The only way to know about the deadline in your case is to call your broker. You should have gotten a letter about the tender, with the deadline included, but their legal responsibility ends when they put it in the mail. They're not responsible for delivering it on time.
If you actually hold share certificates, you should have received the tender documents in the mail. You would still have time to get them to the transfer agent before the deadline tonight.
Lar