Comparison

World Timezone Calendar vs Opti

Price, ratings, monetisation and update history for both apps, side by side — with what reviewers say about each.

Head to head
About

World Timezone Calendar

Easily schedule meetings and events across different time zones. This app helps you find the perfect time for global coordination by comparing multiple time zones and integrating with your existing calendar. Plan ahead with future time views and share events that automatically adjust to recipients' local times.

Highlights
  • Cross-timezone scheduling
  • View calendar in multiple timezones
  • Time travel to plan ahead
  • Add unlimited timezones
  • Day/night indicators
  • Home screen widget
  • Global event sharing
Features
Read full description

Coordinate global meetings, calls, and events without the timezone math. Standard world clocks only tell you what time it is right now. World Calendar goes further: it’s a powerful timezone converter and international meeting planner that lets you look into the future to find the perfect time for everyone. Whether you are scheduling a global team sync, planning an international trip, or calling family overseas, World Calendar integrates directly with your iOS Calendar to make cross-timezone scheduling effortless. CROSS-TIMEZONE SCHEDULING Compare multiple timezones side-by-side to instantly pinpoint the ideal meeting time. Tap anywhere to set a target time, and tap twice to seamlessly create an event directly in your calendar. VIEW YOUR CALENDAR IN MULTIPLE TIMEZONES World Calendar displays your existing events across all your selected timezones. Create, edit, and share events with a single tap, ensuring your global schedule is always perfectly aligned. KEY FEATURES: • Time Travel: Scroll into the future to plan days, weeks, or months ahead. • No Limits: Add and compare as many timezones as you need. • Day/Night Indicators: Instantly see if your contact is awake or asleep. • Home Screen Widget: Check your favorite timezones at a glance without unlocking your device. • Watch Widget and App: Put your recently selected timezones on your wrist • Easy Search: Find locations by city name, timezone abbreviation (e.g., EST, GMT), or UTC offset. • Global Sharing: Send event invites to other users that automatically adapt to their local timezone. • DST Accuracy: Fully automatic adjustments for daylight saving time changes globally. • Nautical Time Zones: Full support for standard UTC offsets without DST adjustments. • Landscape View: Turn your device for a wider, comprehensive timeline view.

About

Opti

Features
Read full description

The Opti-Lock mobile app's primary objective is to address the challenges and risks involved in the delivery of chemicals. In order to safeguard both customers and delivery personnel, chemicals often require specialized handling and transportation, as well as delivery to the right location.

Screenshots

World Timezone Calendar4 screens
Opti4 screens

Verdict

The call

The clearest difference is in-app purchases: Opti at none against World Timezone Calendar's 1. Opti also leads on ads (none vs shown) and update cadence (monthly vs every 4 months). On price and device support there is nothing between them.

Scored on Price · Rating · Positive reviews · Number of ratings · Update frequency · Ads · In-app purchases · Monetization · Best chart rank · Devices · Requires iOS

CostPrice · In-app purchases · Ads · Monetization

Both are free to download. World Timezone Calendar sells 1 one-off in-app purchase. Opti asks for nothing beyond the download.

UpkeepUpdate frequency

World Timezone Calendar ships an update every 4 months, Opti monthly. The most recent releases landed on September 26, 2026 and September 17, 2026 respectively.

Scorecard4 real differences · 6 level
World Timezone Calendar versus Opti: the parameters behind the verdict, then further details
ParameterWorld Timezone CalendarOpti
PriceFreeFree
Rating4.9 (295 ratings) — better—
Positive reviews76.0% of reviews—
Number of ratings295 — better—
Update frequencyEvery 4 monthsMonthly — better
AdsYesNo — better
In-app purchasesYesNo — better
MonetizationFree with in-app purchases—
DevicesiPhone, iPad, Mac, Apple Watch — betteriPhone, iPad, iPod
Requires iOS16.611.0 — better
Further details — not scored
Size19 MB30 MB
Age rating4+4+
DeveloperGeospike Pty LtdHydrite Chemicals

Bugs and requests

World Timezone Calendar

Reported bugs

7 issues
  • 🐛 Inappropriate ads in free version
  • 🐛 Widget settings not saved
  • 🐛 Cannot add new events with double tap
  • 🐛 Timezone abbreviations not displayed
  • 🐛 Search feature doesn't work
Show 2 more
  • 🐛 Crashes when adding a city
  • 🐛 Widget expansion settings not saved

Requested features

5 requests
  • Add more cities
  • Option to freeze time zones for comparison
  • Switch between 24-hour and AM/PM clock
  • Cleaner design with better calendar event integration
  • Ability to pick a specific date to view

Opti

Not enough reviews yet to summarise bugs or requests.

In-app purchases

1 purchases

World Timezone Calendar

One-time1
  • Remove Advertising$19.95
None

Opti

No in-app purchases

Questions

Is World Timezone Calendar free?
World Timezone Calendar is free to download, with in-app purchases available.
Is Opti free?
Opti is free to download, with no in-app purchases.
Do World Timezone Calendar or Opti have ads?
World Timezone Calendar shows ads; Opti does not.
Which is updated more often, World Timezone Calendar or Opti?
World Timezone Calendar ships an update every 4 months, and Opti monthly. Most recently, World Timezone Calendar was updated on September 26, 2026 and Opti on September 17, 2026.

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