今天读到两个例句：
(1)He was visiting an art museum about this time last week.
(2)He was working at McDonald's at that time.
想请问：
1. about 可以用at 或in 替换吗？
2. 1、2句如果交换 意思相同还是会改变？
3. 除了 about/in/at this(that) time
还有其他类似的用法吗？
先谢谢各位前辈了～～～^^

这边 about 应该是大约的意思