Context: Baljeet rings Sunil to ask him about managing the restaurant.
बलजीत - नमस्ते भाई-साहब, सब ठीक तो है?
सुनील - ज़रूर, सब ठीक से चल रहा है, क्या बात है?
बलजीत - मेरा आपसे एक अनुरोध है, क्या आप जुलाई में दो हफ़्ते तक रेस्तराँ संभाल सकेंगे?
सुनील - क्यों? अगर हम आएँगे तो आप लोग क्या करेंगे?
बलजीत - जब आप आएँगे तो हम विवेक की शादी के लिए भारत जाएँगे।
सुनील - अच्छा, हम ज़रूर आएँगे। रेस्तराँ के बारे में तो फ़िकर मत करो।
Baljit - Greetings, brother-sir, everything is well?
Sunil - Certainly, everything is going fine, what’s up?
Baljit - I have a request for you, can you manage the restaurant for two weeks in July?
Sunil - Why? If we come then what will you guys do?
Bajit - When you come then we will go to India for Vivek’s wedding.
Sunil - Okay, we will certainly come. Don’t worry about the restaurant.
In Hindi to link two clauses in a when... then... construction the first clause normally begins with जब and the second with तो or तब. In principle, तब indicates simply the events take place at the same time, whilst तो indicates the event in the second clause is dependent on the event in the first clause. However, in practice, many speakers always use तो whether the two events are causally related or events which simply take place at the same time.
Note that in English the ‘then’ in such sentences is often omitted, but it must be included in the Hindi for such sentences. The tenses in the two clauses normally match in Hindi, in relation to whether the times are past, present or future. But in English there are variations from this.
As mentioned in relation to ‘if’ sentences, when the ‘if’ or ‘when’ is omitted it is often possible to understand a sentence as being either a ‘when...then...’ statement or an ‘if... then...’ statement. The sense overlaps, as it does here.