How many times do you turn knob on timer to set

Test that lights turn on when switch is in ON position. Then turn knob to "TIMER" and set both the time you want the lights to come on then the time for off. Leave knob at "TIMER".

https://www.smarthome-products.com/productspecs/Malibu/8100-0300-01-Manual.pdf
TIMER - The power pack turns on when the clock reaches the TIMED ON time. The power pack will turn off when the clock reaches the TIMED OFF time.

This mode will turn the power pack on and off at the same times everyday regardless of how light or dark it is. The power pack and lights will be on from the TIME ON time to the TIMED OFF time. To set the TIMED ON clock, the knob needs to be turned to TIMER, then hold down the TIMED ON button while pressing either the or button. Pressing while holding down the TIMED ON button will advance the displayed time. Pressing while holding down the TIMED ON button will decrease the time displayed. Holding the or button down for several seconds will speed up the change in the display. Releasing the TIMED ON button will set the time. Note the AM/PM LED indicators to get the correct time of day.
To set the TIMED OFF clock, the knob needs to be turned to TIMER, then hold down the TIMED OFF button while pressing either the or button. Pressing while holding down the TIMED OFF button will advance the displayed time. Pressing while holding down the TIMED OFF button will decrease the time displayed. Holding the or button down for several seconds will speed up the change in the display. Releasing the TIMED OFF button will set the time. Note the AM/PM LED indicators to get the correct time of day

RANGE SETTING THE CLOCK NON-ELECTRONIC CLOCKS: To set the clock:

1. Push the center knob in.
2. Turn the clock hands to the correct time. If the Minute Timer pointer should also move, let the knob out, and turn the Timer pointer to OFF.

DIGITAL CLOCKS: To set the clock:

1. Push in the center knob of the Minute Timer.
2. Turn knob in either direction to set the Digital Clock numerals to the correct time

ELECTRONIC CLOCKS: To set the clock (models with Clock or Set Clock pad):

1. Press the Clock pad
2. Press the + / - pads or number pads (depending on model) to set the time.
3. Touch the Start pad. The time of day will show in the display.

To set the clock (models without Clock or Set Clock pad):

1. Press and hold the + and - pads for 3 seconds.
2. Press the + / - pads to set the time.
3. Touch the Start pad. The time of day will show in the display.

Didn't give a model number, but try the following:

For a mechanical clock, push the center knob in and turn the clock hands to the correct time. (If the Minute Timer pointer should move also, let the knob out, turn the Timer pointer to OFF.)

For a digital clock, push in the center knob of the Minute Timer and turn Knob in either direction to set the Digital Clock numerals to the correct time.

For an electronic clock, touch the Clock pad. Touch the number pad. Touch the start pad until the time of day shows in the display. Note: On double wall ovens, you can only set the Timer for one oven.

(From the GE website)

Didn't give a model number, but try the following:

For a mechanical clock, push the center knob in and turn the clock hands to the correct time. (If the Minute Timer pointer should move also, let the knob out, turn the Timer pointer to OFF.)

For a digital clock, push in the center knob of the Minute Timer and turn Knob in either direction to set the Digital Clock numerals to the correct time.

For an electronic clock, touch the Clock pad. Touch the number pad. Touch the start pad until the time of day shows in the display. Note: On double wall ovens, you can only set the Timer for one oven.

(From the GE website)

Range Setting the Clock and Timer Non-Electronic Clocks: To set the clock, push the center knob in and turn the clock hands to the correct time. (If the Minute Timer pointer should move also, let the knob out, turn the Timer pointer to OFF.)
Digital Clocks: To set the clock, push in the center knob of the Minute Timer and turn Knob in either direction to set the Digital Clock numerals to the correct time.
Electronic Clocks: To set the clock touch the Clock pad. Touch the number pads. Touch the number pads. Touch the start pad until the time of day shows in the display. Note: On double wall ovens, you can only set the Timer for one oven.

Place green tripper at ON time & red tripper at OFF time. Twist timer dial one or more times until current time of day is aligned on pointer. When twisting timer, the trippers should actuate the manual knob on and off each time you make a full turn. Make sure trippers are fully inserted so that they engage the "catch" of the override knob - if not they will not cycle power to the output.

To set the time, turn and hold the Timer knob to the clock
symbol = and at the same time turn the Adjusting knob left
or right until the clock shows the time of day. Remember this
is a 24-hour clock. Let go of the Timer knob and it will spring
back to the vertical, oven manual setting.

I cannot find a manual for the Darlac DW253.
It appears the timer is set by moving each selector knob.
http://www.watermate.co.uk/secure/uploads/DW253%20(Small)%20new%20darlac%20pop.jpg

Knob on right is Run Time:
This is how many minutes timer will run each time.
Set run time from 1 minute to 120 minutes.
Knob on right also has ON-OFF override.

Knob on left is Frequency:
This is how frequently the timer will turn ON. Once per hour, once per each 2 hours ... once per 24 hours ... once per 72 hour ... once per week.

So set frequency to 48 and set run time to 20, then every 48 hours the water will turn on for 20 minutes.
To turn timer off, move right knob to OFF.
For continuous watering, turn same knob to ON.

This timer is battery-powered, probably 9 Volt, but maybe AA.
Battery carriage appears to be located on front below the function knobs.
Typically, water timer batteries last one season.

Timer can be connected to household spigot, or connected to any passive water supply for example rain barrel or tank.
Appears to have standard female hose thread on top, or possibly 1/2 pipe thread, and quick connection on bottom.

Plastic water timer exposed to freezing temperatures can crack. Drain water out of timer during cold weather.
Generally if water timer stops working: replace battery, clean battery terminals, and if functionality is not restored, then buy another timer.

Add a comment to fill out the missing details.

http://www.rangemaster.co.uk/Siteimages/Site_311/Pdf/ProfessionalPlus110DFOct08.pdf
User manual.
When the clock is first connected, the display flashes ( 0.00) and (?) alternately. To set the time, turn and hold the Timer knob to the clock symbol (?) and at the same time turn the Adjusting knob left or right until the clock shows the time of day. Remember this is a 24-hour clock. Let go of the Timer knob and it will spring back to the vertical, oven manual setting.
It is on page 6 of manual

call manufactuerer and ask if you can order one or try to do so online