Learn Hardcore German: Ich bin heute bis 18 Uhr erreichbar, solange die Kinder schlafen. - I am reachable today until 6 p.m., as long as the children are sleeping.

Erreichbar means contactable/reachable (typically by phone, message, or email). It says nothing about physical distance, only whether you can get hold of the person. Close relatives:

verfügbar: available/free to help or to be scheduled; also used for items in stock.
ansprechbar: responsive, approachable (e.g., not asleep, not sedated).
zu erreichen: alternative phrasing for the same idea, e.g., Ich bin bis 18 Uhr zu erreichen.

Is the comma before solange required?

Yes. Solange introduces a subordinate clause, and German requires a comma before such clauses: Ich bin … erreichbar, solange ….

Does solange make the verb go to the end?

Yes. In subordinate clauses, the finite verb goes to the end: solange die Kinder schlafen. In the main clause you still have verb‑second: Ich bin heute … erreichbar.

Can I move the solange-clause to the front?

Yes: Solange die Kinder schlafen, bin ich heute bis 18 Uhr erreichbar. When a subordinate clause comes first, the following main clause starts with the finite verb (bin ich), not ich bin.

How is solange different from während or wenn?

solange: for the entire duration of the other event; often has a conditional feel. Ich bin erreichbar, solange die Kinder schlafen suggests availability only while they’re asleep.
während: simply at the same time; no condition implied. Ich bin erreichbar, während die Kinder schlafen emphasizes simultaneity.
wenn: when/if; focuses on the time point or condition, not duration. Ich bin erreichbar, wenn die Kinder schlafen can sound like you’re only reachable whenever that condition happens.

What’s the difference between solange and so lange?

solange (one word) is a subordinating conjunction introducing a clause: Solange die Kinder schlafen, …
so lange (two words) is an adverbial phrase meaning for that long, often with wie: Ich bleibe so lange, wie es nötig ist. You cannot replace solange with so lange unless you also add wie and adjust the structure.

Does bis 18 Uhr include 18:00 exactly?

In everyday German, bis 18 Uhr means up to 18:00 and not after. It is usually understood as stopping at 18:00. If you need to be explicit:

Inclusive: bis einschließlich 18 Uhr or noch bis 18 Uhr.
Exclusive: bis kurz vor 18 Uhr or nur bis 17:59 Uhr (very literal).

Is bis um 18 Uhr correct?

Yes, you will hear it a lot, and it’s acceptable in informal German. Many style guides prefer the leaner bis 18 Uhr in neutral or formal writing.

Why not bis zur 18 Uhr?

With clock times, German uses a bare time expression without an article: bis 18 Uhr, bis 6 Uhr. You only use an article with bis when another preposition is added, for example with dates: bis zum 18. Juni. So bis zur 18 Uhr is unidiomatic.

Why present tense (bin) if it includes the future part of today?

German often uses the present tense for scheduled or near‑future events when a time expression makes the timing clear: Ich bin heute bis 18 Uhr erreichbar.

Where should the time expressions go? Is heute bis 18 Uhr the best order?

Yes. When you have several time adverbials, German tends to go from general to specific. heute (the day) before bis 18 Uhr (the exact limit) sounds natural: Ich bin heute bis 18 Uhr erreichbar. You can front Heute for emphasis: Heute bin ich bis 18 Uhr erreichbar.

Is Uhr necessary? Can I just say bis sechs?

In speech, bis sechs is common and fine.
In writing or for clarity, bis 18 Uhr is standard. If you use 12‑hour times, add a clarifier: bis 6 Uhr abends.
18 Uhr or 18:00 are both acceptable formats in German.

What case is die Kinder, and why?

Nominative plural. It is the subject of the subordinate clause (die Kinder schlafen). The verb agrees in 3rd person plural (schlafen). The article die is the plural definite article.

Can I drop the article and say solange Kinder schlafen?

Yes, but it changes the meaning: solange Kinder schlafen sounds generic (whenever children sleep in general). solange die Kinder schlafen points to specific, known kids (very likely the speaker’s own).

Is Ich bin heute bis 18 Uhr zu erreichen the same as using erreichbar?

Practically yes. zu erreichen is a passive‑like alternative and is slightly more formal or service‑like. Both are idiomatic: Ich bin bis 18 Uhr erreichbar / Ich bin bis 18 Uhr zu erreichen.

Should it be schlafen or schlafen werden for a future meaning?

Use simple present schlafen. German does not use werden in subordinate time clauses like this to mark future. The time adverbials already locate it.

Why are Kinder and Uhr capitalized?

All nouns are capitalized in German, so Kinder and Uhr are capitalized. Adverbs like heute are not.

Any quick pronunciation tips for tricky words here?

erreichbar: stress on reich; the ch is the soft ich‑sound [ç]. The final r in -bar is often weak.
solange: stress on -lan-; g is [g], not [dʒ].
Uhr: long u ([uː]); many speakers weaken the final r.