Tarkistettuani varauskalenterin varasin pyykkivuoron myös ensi keskiviikolle.

It means after I checked or having checked.

In this sentence, tarkistettuani varauskalenterin gives the background action that happened first, and varasin pyykkivuoron... is the main action that happened after that.

So the timeline is:

1. I checked the reservation calendar.
2. Then I booked a laundry slot.

This kind of form is a very common Finnish way to say after doing something.

It is built from the verb tarkistaa and a special temporal construction:

• tarkistaa = to check
• tarkistettua = checked / after checking
• -ni = my / I

Together, tarkistettuani means after I had checked.

A very important point: the -ni shows that the person doing the checking is I, and that same person is also the subject of the main verb varasin.

So Finnish can pack a lot of information into one word here.

Because Finnish often leaves out the subject pronoun when it is already clear from the verb form.

Here, the sentence shows first person singular in two places:

• varasin = I reserved
• tarkistettuani = after I checked

So minä is unnecessary. You could add it for emphasis, but normally you would not.

They are both objects, and here they are in the total object form, which in the singular usually looks like the genitive ending -n.

• varauskalenteri → varauskalenterin
• pyykkivuoro → pyykkivuoron

Why this form?

Because both actions are understood as completed whole actions:

• I checked the reservation calendar as a whole.
• I reserved one complete laundry slot.

If the meaning were incomplete, ongoing, or partial, Finnish might use the partitive instead instead of -n.

It is a compound word:

• varaus = reservation, booking
• kalenteri = calendar

So varauskalenteri means reservation calendar or booking calendar.

Finnish uses compound words very freely, so long words like this are very normal.

It is another compound:

• pyykki = laundry
• vuoro = turn, shift, slot

So pyykkivuoro literally means something like laundry turn, but in natural English it usually means a laundry slot or a reserved time to use the laundry room / washing machine.

This is especially common in apartment buildings or shared laundry facilities.

Because varata often uses -lle when you book something for a certain time.

• ensi keskiviikolle = for next Wednesday
• ensi keskiviikkona = on next Wednesday

That is an important difference.

In this sentence, the booking happens now or earlier, but the laundry slot is for next Wednesday. That is why -lle is used.

So:

• Varasin ajan perjantaille = I booked an appointment for Friday.
• Menen perjantaina = I’m going on Friday.

Yes, here ensi means next or coming.

• ensi keskiviikko = next Wednesday

In everyday Finnish, ensi is very common with days, weeks, months, and similar time expressions.

Depending on context, English next Wednesday can sometimes be ambiguous, and Finnish can also depend a little on context, but normally ensi keskiviikko means the upcoming one that comes next.

Myös means also or too.

Here it shows that booking the laundry slot for next Wednesday was an additional action or an additional booking.

The nuance is roughly:

• I booked a laundry slot also for next Wednesday.

So the speaker is implying that some other booking already existed, or that next Wednesday was added in addition to something else.

Its placement before ensi keskiviikolle makes the time expression the thing being added.

Because it sets the scene for the main action.

Finnish often puts this kind of background information first:

• Tarkistettuani varauskalenterin = after checking the reservation calendar
• varasin pyykkivuoron myös ensi keskiviikolle = I reserved a laundry slot also for next Wednesday

This order is very natural and helps show the sequence clearly.

English does the same thing quite often:

• After checking the calendar, I booked...

Yes. A learner-friendly alternative would be:

• Kun tarkistin varauskalenterin, varasin pyykkivuoron myös ensi keskiviikolle.
• Tarkistin varauskalenterin ja varasin pyykkivuoron myös ensi keskiviikolle.

These are more explicit and may feel easier at first.

Compared with those, Tarkistettuani... is more compact and slightly more formal or written in style, though it is still perfectly normal Finnish.