The one year grace period provided in U.S. patent law for at least the past half century never coincided with foreign patent law. In short, there is, and remains, a lack of a clear foreign grace period. Some countries provide the same one year grace period (prior to the most recent change in September 2011), but for different activities, other than offer for sale or public use. Some countries offer a grace period for offers for sale or public use, but for a shorter time period. Some countries offer no grace period. Keeping up with all the different countries and their differing, or nonexistent, grace periods can be a momentous task---among other things, other countries pass and modify laws the same as our country--so to a certain extent, a moving target aspect exists.
This complexity was somewhat mitigated, but also exacerbated, by the international treaty that provided that filing a foreign patent application within one year of filing a domestic patent application (and claiming priority to the domestic patent application) allowed the foreign application to have the effective date of the domestic patent application, i.e., one year earlier.
The result of that treaty was the creation of two one year bars. The US public use/offer for sale one year bar, and the foreign patent filing claiming prior to the US patent application one year bar. but the foreign patent application may not have the same grace periods that the US patent application enjoyed, so even though the foreign patent application was filed within one year of the US patent application (and claimed priority to it), the foreign application may still be invalid if the inventor engaged in public use or offers for sale within the one year prior to filing the US patent application, even though the US patent application would not be invalid. Confused enough? It's like a bizarre Rube Goldberg machine.
As a general rule, with many exceptions that your patent attorney will have to research, do NOT rely on the existence of any foreign grace period.