How long would it take to reach the farlands by walking?

To calculate the time it will take to walk to the Far Lands, we need to know two things, the speed that Steve walks, and how far it is to walk there.

Speed

According to the "Sprinting" page on the wiki, the normal walking speed of Steve is around 4.317 m/s.

Distance

From the "Far Lands" page on the wiki:

In the Minecraft: Pocket Edition 0.9.0 beta series, a Far Lands similar to the PC edition exists about 12,550,745 blocks from spawn.

Calculation

Time = Distance / Speed

Time = 12,550,745 / 4.317

Time ≈ 3033779 seconds

Time ≈ 842 hours

Time ≈ 35 days

Notes

We have calculated that it would take you approximately 35 days to walk to the far lands in Minecraft: Pocket Edition. But it is unlikely you would make it this far, according to the "Far Lands" page on the wiki, there a few things that will happen before you make it to the Far Lands:

• Gaps between chunks first begin to be noticeable at X/Z values above 100,000.
• At around X/Z: 700,000 "jitteriness" is experienced and the world starts to become glitchy and unplayable. Chunks are seen to vibrate rapidly.
• Past X/Z: 900,000 the world becomes completely unplayable and crashes are very frequent at this point.

But if you do make it to the Far Lands, you will come across something similar to this:

Image from the Minecraft Wiki.

Given that the player walks at 4.3 m/s (unless you'll be able to sprint) and the Far Lands are 12,550,821 blocks/meters from the origin, it will take you 820 hours or 34 days of walking to reach them. Source: Minecraft Wiki