I don;t like this much. There is easier ways how to achive this
1) slower but correct invert
```
def update_timezone
  region_entries.invert[timezone]
end
```

2) slightly longer but still correct
```
def update_timezone
  region_entries.each_pair {|k,v| return k if v == timezone }
end
```

3) native methods, but it change in 1.9 so it need some handling
```
def update_timezone
  return region_entries.respond_to? :key ? region_entries.key(timezone) : region_entries.index(timezone)
end
```