HI David,
Thank for your comments,
Look at gmail login page, where also we have same type of field, "user name" and "password". See how nicely it working with out giving any confuse for the user.
Still you are not sure what's 4 that "checkbox". Being a User Experience Architect you are still guessing that, this may be for "remember me" option. (Then you think about a normal user!)
Yesterday option is ok. Each time we cannot change time setting as you said. Let the system take the risk, why should i change the time day by day once i set my region.
There are people who use 08:40 AM for morning and 08:40 for Evening.
Hope! you know the meaning of AM and PM. If not please see this en.wikipedia.org/wiki/Ante_Meridiem
After All we are not going to loose anything by giving clear information to the end user. All Usability Gurus says that "never make the user to think". So David take little more time before you comment and assess. And would appreciate if you could not use unparliamentary words.