How do you change the timings on a Diall EMT551ET timer switch?

Instruction manual. English starts on page 27. These digital timers are very complicated. You have to have the timer in one hand and the instructions in the other.
https://cdn.leroymerlin.ro/document/11554/61dd68a8f306e_20220111012320.pdf?p=0

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Intermatic T174 wires exactly like the T104 240Volt timer.
Only difference between T174 ans T104 is the day skipper wheel on T174.
http://waterheatertimer.org/How-to-wire-T104-Intermatic-timer.html#T104

These timers are very versatile and can be wired many ways, and changed to control different voltages by changing clock motor wires, or changing clock motor.
Voltages include typical 240Volt. But also 277V, 480V, 120V, 208V and 24Volt

If you need further help, I’m available over the phone at https://www.6ya.com/expert/gene_9f0ef4df2f9897e7

Slide switch on bottom left to TIME. Press H key for hour - M key for minutes Then WEEK key until day of week. Press SET and current time is displayed. Slide bottom left switch back to AUTO and present time will display

First press reset (use pen or paperclip). Press MOVE button until you get OFF at right bottom of screen, then press SELECT to select mode (to set time and date, to select on/off for the 2 timers or to select rundown timer. Use OK to move to different setting, eg. hour,minute, year,month day etc. Use SELECT to change up one digit at a time. Play around with buttons to change settings, for example to have timer on on a specific day of the week or everyday etc. When it is set, use move to change from OFF to AUTO, timer will then switch on and off at set times. Hope it helps

N1505 timer manual:
http://waterheatertimer.org/pdf/Woods-49122-N1506-manual.pdf

N1506 is heavy duty outdoor timer with display screen.
Plug timer in and display flashes C.
Set current time: press Time button once and display shows 1 am
Keep pressing time button until current time with am pm displays.
Dot in lower right corner corresponds to pm hours.

To set timer program:
Press Mode button, display flashes P
Press Time button until desired ON time displays.
Press Mode button again and display flashes E
Press Time button until desired OFF time displays
When programming is finished, press Mode button and display shows current time.

To reset timer, unplug timer for 10 seconds and re-program timer.
Timer must be reset after power outage. Display will warn by flashing C.

Plug lights into timer.
If lights have a switch, switch must be on.

For manual override, press Mode button, and display shows O and lights will be ON until next program change.
To use timer function, press Mode button until current hour displays.

N1505 timer manual:
http://waterheatertimer.org/pdf/Woods-49122-N1506-manual.pdf

N1506 is heavy duty outdoor timer with display screen.
Plug timer in and display flashes C.
Set current time: press Time button once and display shows 1 am
Keep pressing time button until current time with am pm displays.
Dot in lower right corner corresponds to pm hours.

To set timer program:
Press Mode button, display flashes P
Press Time button until desired ON time displays.
Press Mode button again and display flashes E
Press Time button until desired OFF time displays
When programming is finished, press Mode button and display shows current time.

To reset timer, unplug timer for 10 seconds and re-program timer.
Timer must be reset after power outage. Display will warn by flashing C.

Plug lights into timer.
If lights have a switch, switch must be on.
For manual override, press Mode button, and display shows O and lights will be ON until next program change.
To use timer function, press Mode button until current hour displays.

Hi. this will usually be a defective timer module issue. replacing the timer will fix this issue.

This timer only works with incandescent light bulbs. It does not work with CFL's (compact flourscent light bulbs). Intermatic model ST01C will work with CFL's and LED's. I ordered one today from WestsideWholesale.com. They had the best price.

If you dialed feature 00 to access the mode, you must diall feature 00 to exit which will save information.

Locate the COMMON wire
connected to first old switch.
It might be attached to a different
colored screw, or find
markings on old switch.
Connect BLACK wire from
switch timer to COMMON
wire, using a twist connector.
Connect the other two wires from the old switch to either the
BLUE and RED wires from the switch timer.
Connect the ground wire from the box to the BARE COPPER
wire on the switch timer. If there is no ground wire, ground the
switch timer to the box. If the box is plastic, connect the bare
copper wire to ground as supplied or contact an electrician.
Locate the COMMON on the second old switch of the 3-way pair.
Connect jumper wire (supplied) from the COMMON terminal
to either of the other terminals on the remote 3-way switch.
Make sure all twist connectors are tight.
Tuck wires into wall boxes leaving room for the devices.
Mount the devices into the wall boxes, then install the wall plates.
Turn power back on at the service panel.
Make sure the switch timer displays “MAN” mode. Do the following
test with the remote switch in each of its 2 positions:
Press the NEXT ON/OFF button on the switch timer several
times. Each time that you push the NEXT ON/OFF button, the
switch controlled light or device (the “load”) should turn on
or off. If so, proceed to Section 3.
If the timer display changes between ON and OFF but the
load does not operate, re-check your wiring and make sure
the load is functional.
If the timer display changes
between ON and OFF but the
load only operates when the
remote switch is in one of
its 2 positions, you need to
turn off the power at the service panel, change the jumper
wire to the other terminal. Then turn power back on at the
service panel and repeat. good luck