It is all one a hundred years hence.

From the long view of a century, the present difference will cease to matter. The saying urges detachment from immediate disputes, disappointments, or anxieties by placing them against the eventual passing of time.

It can also express resignation: whichever outcome occurs now, both parties and their concerns will be gone in the distant future. That perspective may console, but it can sound dismissive when used to wave away a real present harm.

Use it when stressing that a current choice, quarrel, or setback is unlikely to retain importance over a very long span. It suits reflective or fatalistic remarks more than practical advice, and should not be directed at someone facing serious present suffering or a responsibility requiring action.