This summer Google Adwords plan to give an access to the Adwords and MCC account owners to set their accounts'time zone. By doing this they probably want to make sure that all metrics returned for a given account will be registered in that account's time zone (currently all accounts are reported in US Pacific Standard Time (PST)-the time zone for Google's headquarters in California). To add more, the billing and budgeting cycles will depend upon each account's time zone.
However, the advertisers and MCC managers are said to be invited to set their time zones in the coming month of May. It is further concluded by Google that they will introduce a new version of the Adwords API which comprise of "set" and "get" time zone features. A detailed/technical FAQs (via the Adwords API Blog) session will also be a part of their release.
From Google Adwords :
What is Time Zone Support?
Advertisers can select any time zone in the world for their AdWords account. All reporting, ad serving, and billing will be based on the time zone set by the advertiser. Advertisers or MCC managers who choose not to establish account time zone settings will continue to have their accounts managed in US PST, as they have been in the past. It is important to note that each account's time zone may only be set once, so advertisers should be careful when setting their time zone.
Will this change be backward-compatible with V3?
Once you begin setting time zones for your accounts, you will still be able to use the current version (V3) of the API. However, there will be one difference. In V3, all API calls will still return account statistics in PST (regardless of each account’s specified time zone) except for reports, whose day boundaries will be calculated in each account’s local time zone.