MT5 Calendar data bug

I've hit a bug so infuriating, I'm looking for help.
The MT5 calendar data downloads from a different server / route from standard price data but appears sketch AF.

You need to be logged in - check.
But it's so intermittent it often returns no records.
Is this a MT5 demo server limitation? The events appear in the terminal, just not via download around 50% of the time. and I've no idea what's different when it works vs not.
Do I just need a live account elsewhere for improved reliability? I can do that but the config will take me yonks, so if anyone knows before I take the plunge...

personally I’ve never used the calendar data in MT5, I pasted your post into DeepSeek and got this, hopefully it’s helpful:-

The short answer is yes, a live account is very likely to make your calendar data much more reliable. But I'd recommend holding off on that just yet, as there are a few simpler things you can try first.
Is this a Demo Server Limitation?
In short: yes, this is very likely the core issue. While Demo accounts mirror live market data, they often use different backend infrastructure with lower priority access. For non-trading data (like the economic calendar), servers are more susceptible to rate limiting, timeouts, and sync delays (leading to your 50% failure rate).
What to Check Before Switching
Inconsistent results often hide in these areas:
· Date Range Timeouts (ERR_CALENDAR_TIMEOUT, 5401): The CalendarValueHistory function has a known issue—it frequently fails if the date range exceeds 30 days. Try narrowing it to month-by-month and add retry logic.
· First Request vs. Cached: The terminal can time out or return empty results if you request data too soon after launch. Wait for the terminal to sync or just re-run the script.
· Strategy Tester: The Strategy Tester has no live server connection. The calendar data will not work there. You must switch to a CSV fallback method for backtesting.
· DNS / Network: In some rare cases, your local DNS might struggle to resolve MetaQuotes economic calendar servers, causing failures.
Mitigation Strategies
If adjusting the logic doesn't fully solve it:
· Add Retry Logic: The simplest fix. If CalendarValueHistory returns zero, wait a few seconds (e.g., Sleep(5000)) and try again (up to 3 times).
· Use a CSV Fallback: Manually export the calendar to CSV (using a script) and have your EA read that static file. It’s the most reliable method for stability.
· Check Your Broker: Sometimes brokers limit calendar data on their demo servers. Try opening a free demo with a different broker to see if the issue persists.
Upgrading to a Live Account
If nothing else works, moving to a live account is your best bet. Production servers have far less strict throttling and dedicated resources for data delivery. If you go this route, be aware that you’ll need to reconfigure for the live server and test thoroughly in a low-risk environment first.
Hope this helps you tame that bug. Which function are you currently using to pull the data? Knowing that might help narrow down the best fix.

· Date Range Timeouts (ERR_CALENDAR_TIMEOUT, 5401): The CalendarValueHistory function has a known issue—it frequently fails if the date range exceeds 30 days.

et voila - yeah it's 2 years data. This is one of the reasons I should have done it all in python with a DB backend so I could append data rather than load from fresh. Thanks fella - funnily enough GPT was straight into coding solutions rather than taking a step back so useful info.

Maybe the way I prompted it, I literally pasted your post, glad you found the solution.

I must say Deepseek in Deep thinking mode is my go to for most things, very few errors in my experience.


In terms of architecture and the separation of concerns, I prefer to use MT4/5 for what it is really good at, broker interface, execution and trade management, so my instinct would have been to interface with the calendar using a Python process and feed the results into the EA in an easily digestible form such as CSV, but beware I've come across anomalies even reading CSV files with MT4/5. My trade management system which complies on both MT4 and MT5 using conditional preprocessing (#ifdef etc) is some 7k lines now, it is a beast!

You're both right and late

I don't execute through MT5, but I stuck all the processing and display and data all in one indicator with persistent and sometimes sketchy caching. It works. just. But even with my noddy skills I can see where I've made life hard for myself.

Everything should be platform and broker agnostic; except for display overlays and explicit API connections to your broker that can be changed on a whim. that was only clear once I'd learnt some very basic programming stuff.

At some point, I'll move into vps/python/modular set up, I'm just spending so bloody long on it all, I'm taking a breather for a while on the heavy dev.

Well good luck with it all, it sounds very interesting and as mentioned in the other thread https://www.forexfactory.com/thread/...tative-trading I must find time to play with it too, please keep me posted