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Two Japan plans can both say “30 days” and still need to be bought at different times.
In our current range, the 3GB plan has 180 days to start. The 10GB plan has 60. Both have 30-day validity once started. That difference matters a lot more than the size of the discount if you’re shopping in November for an April holiday.
I run The SIM Shop. Here’s how I’d work out the timing, and what I’d do with the setup email once the purchase is sorted.
The number in the plan name isn’t the whole deadline
There are two separate questions: how long can I keep this before starting it, and how long will it last once I do?
“30 days” answers the second question for the Japan plans below. Their start windows answer the first. Buying a 30-day plan doesn’t mean you must use all of it in the 30 days after paying. It also doesn’t mean you can leave it unused indefinitely.
Here’s the comparison using our announced Black Friday offers. The start windows and previous listed prices were checked on 27 October 2026.
Pre-sale preview for 20 to 30 November 2026. The sale hasn’t started yet; these upcoming prices aren’t available now. All amounts are AUD.
Scroll sideways to compare
| Japan plan | Time to start after purchase | Previous listed price | Upcoming Black Friday price, from 20 November | Discount |
|---|---|---|---|---|
| 3GB / 30 days | 180 days | A$11.95 | A$5.40 | 55% off |
| 10GB / 30 days | 60 days | A$19.95 | A$9.90 | 50% off |
Percentages are rounded to the nearest whole number. Separate current promotions can have different prices and terms. We’ll recheck the comparison prices, plans and conditions before the campaign opens. Follow the deadline supplied with the exact plan you buy.
Notice the smaller plan has the longer start window. You can’t carry one plan’s rule across to another just because they’re for the same country.
Put the purchase and arrival dates on a calendar
Suppose you buy on 20 November 2026. These examples show the gap until you’d first need data overseas.
| First use overseas | Gap from 20 November | What that means for a 60-day start window |
|---|---|---|
| 20 December 2026 | 30 days | Within the window; check the plan lasts for the trip too. |
| 10 January 2027 | 51 days | Within the window, but allow for any change of dates. |
| 10 April 2027 | 141 days | Outside the window. Leaving it unused won’t extend it. |
For that April example, the 3GB plan’s current 180-day start window reaches the intended first use. That only solves the timing question. If 3GB won’t cover the holiday, I’d choose a suitable alternative or buy closer to departure. A longer start window doesn’t turn a small allowance into a bigger one.
Count days rather than rounding to months. From 20 November to 20 May is 181 days, so “six months ahead” can already be too early for a 180-day window. The exact deadline supplied with the plan controls, including any time-of-day cutoff. I wouldn’t aim for the very last permitted day if the trip could move.
Buying early doesn’t mean installing early
You can buy, save the email and leave the installation until you arrive. For our plans, that’s the setup route we want you to follow.
Before departure, check your exact phone supports eSIM and is unlocked. Keep the setup email somewhere easy to find. If you’re buying for several people, make sure each person knows which email or eSIM belongs to their phone.
After landing, join airport Wi-Fi, complete its sign-in and load a normal webpage to check the connection. Then open the SIM Shop setup email and install. If that Wi-Fi won’t work, wait for hotel Wi-Fi or another steady trusted connection.
Don’t scan the QR code or tap Quick Install before the trip just to see whether it works. You can check compatibility without installing the eSIM. Installation can also change refund eligibility.
Leaving the email untouched doesn’t pause the purchase-to-start window, though. Buying and installation are separate steps; the deadline can still arrive while you haven’t installed anything.
Check how the last day is counted, too
Once the start window works, make sure the plan covers the end of your trip. Calendar days and full 24-hour periods aren’t the same thing.
Our local KDDI range counts the date of first KDDI data use in Japan as Day 1, even if you start at 11pm. Service ends at 11:59pm Japan time on the final calendar day. It doesn’t give you a full extra day just because you arrived late.
That range also has a supplier-issued start-by deadline, rather than the 60- or 180-day rule in the fixed-data comparison above. Read the local KDDI terms and the deadline supplied with the exact plan. Other plans and retailers can use different start events and expiry rules.
If the dates move after you’ve bought
Check the new first-use date against the actual deadline before doing anything to the eSIM. If it no longer fits, contact us before installing it. Include the order number and new travel dates so we can look at the right plan.
For qualifying paid orders during our upcoming Black Friday campaign, the change-of-mind promise will give you 365 days from purchase to request a refund while the eSIM remains uninstalled, unactivated and unused. Guest orders are included; the refund is the amount actually paid to the original payment method unless you choose another lawful remedy. See the full refund conditions. Australian Consumer Law rights apply separately.
Those 365 days are time to request an eligible refund. They aren’t extra time to start the plan.
If your dates are settled and the plan reaches them with room to spare, buying ahead can get one job off the list. If they don’t, I’d buy later. The Black Friday offers are planned for 20 to 30 November 2026, with their own terms; current selected-plan prices and any separate offers apply until the campaign opens. Our waiting guide helps decide whether to hold off until then.
