Gravity affects time dilation, and the strength of gravity needed for significant time dilation depends on the context. In general, time dilation occurs in the presence of gravitational fields, as described by Einstein's theory of general relativity.
According to general relativity, time runs slower in a stronger gravitational field compared to a weaker gravitational field. This effect is known as gravitational time dilation. For significant time dilation to occur, the gravitational field strength should be relatively intense.
Near massive objects, such as black holes or neutron stars, where gravity is extremely strong, time dilation can be substantial. In these extreme cases, the gravitational field is intense enough to cause noticeable effects on the flow of time. Clocks closer to the massive object would appear to tick slower compared to clocks farther away.
However, even in less extreme scenarios, there can still be measurable time dilation. For instance, on Earth's surface, the effect is relatively small but detectable. Clocks situated at higher altitudes, where the gravitational field is slightly weaker, run slightly faster compared to clocks at lower altitudes.
In summary, any gravitational field, no matter how weak, will have some effect on time dilation. However, for significant time dilation to occur, the gravitational field needs to be strong, typically in the vicinity of extremely massive objects.