[Gravity can alter wavelength of energy body/particle.]
In physics and relativity, time dilation is the difference in the elapsed time as measured by two clocks. It is either due to a relative velocity between them or to a difference in gravitational potential between their locations. When unspecified, "time dilation" usually refers to the effect due to velocity. Dilation means enlarged or stretched or expanded or widened. So Time Dilation means time enlarged or time stretched or time expanded or time widened.
In the theory of special relativity, the “slowing down” of a clock as determined by an observer who is in relative motion with respect to that clock. There are several direct proofs of time dilation. Extremely accurate clocks have been flown on jet aircraft. The clock in motion shows a slightly slower passage of time than the one at rest.
However, the "time" of the entire Universe can be a single "frame of reference" and there is no need to use two different frame of references - as considered in the phenomenon of "time dilation" - as "time dilation" actually represents "wavelength dilation."
The mathematics and result of practical experiments behind the subject concerned, when energy body/particle are affected by gravitational stress exerted on them, accordingly wavelength of the energy body change.
Plank's equation presents energy is proportional to its frequency E∝ Frequency, and frequency of a wave is inversely proportional to its wavelength f∝1/λ and, frequency of a wave is inversely proportional to its time period f∝1/T. Therefore the wavelength of a frequency is directly proportional to the wavelength’s time period λ∝T.
This means when wavelength change time period also change, if time period change then there will be difference in time too.
Besides this phenomenon is supported by the General Relativity, in general relativity gravitational red-shift is the phenomenon in which electromagnetic waves or photons travelling out of a gravitational well will lose energy resulting the photon's longer wavelength affected by the gravity. This gravitational red-shift will cause wavelength enlargement of the wave of the mass-frequency of a body under consideration.