How to store and calculate number of hours or days?

Questions & Help
1

In an advanced flow, how do I use a variable to calculate number of hours or days compared to current time?

I want to create some smart(ish) flows for my robot vacuum cleaner.

Some example scenarios:

Scenario 1: Instead of a automatically start cleaning on a fixed schedule, I want only let it run based following criteria:

  1. Nobody is currently at home.
  2. It has been at least 3 days sense last completed run.
  3. The mop is dry (at least 3 hours after last time completed mopping run).

Scenario 2: Don’t vacuum the bathroom if someone have showered X hours ago. I don’t want to let the vacuum potentially wet floors, so I want it wait until the water have evaporated.

As I see it, the ideal way to solve this, if possible, is to calculate timestamps of dates in a (advanced) flow.

I’m open for suggestions, but I would prefer to solve this either with standard Homey features or with well maintained and versatile community app (I try to avoid to install apps in general).

2

There are cards (WHEN Last person left home) , but that is not really reliable, at least not at my home. There Are some threads about this issue, just search.

You do not need to calculate, just use a timer.
When mopping stops
*Then
Set mop_is_dry to NO
Start Timer MoppingDone with 3 hours

WHEN Timer MoppingDone finishes
Set mop_is_dry to YES
etc.

3

Thank you for the timer/delay tip.

However, I’m a bit concerned about what happens if there’s an unexpected hub shutdown (e.g., due to a temporary power cut). Do timers survive restarts?

Also, this doesn’t fully address the core issue:

“It has been at least 3 days since the last completed run.”

As far as I can tell, delays are limited to 999 minutes (~16 hours), which isn’t sufficient for multi-day checks.

Additionally, I may want to trigger different actions depending on how long it’s been :

  • After 5 days: send a reminder message.
  • After 7 days: start vacuuming anyway.
  • After 10 days: call my parents and force me to clean my home (just kidding… kind of).

So having access to timestamps or being able to compare the current time to a stored value would make the logic much more flexible.

4

:cross_mark: onboard delays don’t; I"d use them for small delays (seconds) only
:white_check_mark: timers from the Chronograph app do, while they count up towards a timestamp, set by the “duration” value.

The other things you mention can also be done with Chronograph timers. It has a “day” unit for instance, so no calculations with seconds or minutes needed.
These timers can delay for 999 days, maybe even longer:

Screenshot_20250716_190722_Firefox
Screenshot_20250716_190722_Firefox976Ă—299 44.9 KB

See it counting down:

Screenshot_20250716_191023_Firefox
Screenshot_20250716_191023_Firefox861Ă—735 112 KB

You can count hours, or days etc. with variables as well:

When..
every day
Then..
calculate numeric var “vac” as {{ [var] +1 }}

This increases the variable’s value by 1 each day.
(at some point, reset it to 0 again)

Now you can trigger flows based on that number

When..
variable “vac” has changed
And..
logic card value “vac” is exactly 3 (or 5 or 9 or 400)
Then..
Do things

or:

When…
the last person left
And..
logic card value “vac” is exactly 3 (or 5 or 9 or 400)
Then…
-go vacuum
-logic card set variable “vac” to 0

When you really want to calculate with timestamps, I’d recommend to read the Better logic library app topic.

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5

Thank you for your reply, really helpful.

I decided to go with the Chronograph app for this setup.

Current setup:

  1. A Chronograph stopwatch tracks the time since the last completed vacuum run.
  2. When the flow is triggered (e.g. nobody is home), it checks the stopwatch duration:
  • If it’s more than 3 days, a vacuum job is started, and a "cleaning in progress” Chronograph timer is started (set to 1 hour).
  1. When the robot reports “Finished cleaning”, the flow checks if the “cleaning in progress” timer is still running:
  • If it is: it stops/resets both the timer and the stopwatch.

The purpose of the “cleaning in progress” timer is to distinguish automated runs (triggered via Homey) from manual or spot cleaning.

Since I can’t directly determine the type of cleaning job completed, this acts as a temporary self-clearing flag indicating that a Homey flow initiated the vacuuming.

This setup is less than a day old, so I haven’t tested it in real-world use yet, but initial manual testing of the flows looks promising.

2 Likes