2 replaced http://english.stackexchange.com/ with https://english.stackexchange.com/
source | link

I've read the questionthe question about Future Simple and Future Perfect, but I still can't understand the exact usage of these two tenses.
Is there any diffrence between the following?

I will do my homework by 6 p.m.
I will have done my homework by 6 p.m.

I will do my homework after school
I will have done my homework after school

Also, I've checked the word 'by' in Oxford dictionary and there're some confusing examples:

By the time (that) this letter reaches you I will have left the country.

Can I use 'By the time (that) this letter reaches you I will leave the country' instead?

I've read the question about Future Simple and Future Perfect, but I still can't understand the exact usage of these two tenses.
Is there any diffrence between the following?

I will do my homework by 6 p.m.
I will have done my homework by 6 p.m.

I will do my homework after school
I will have done my homework after school

Also, I've checked the word 'by' in Oxford dictionary and there're some confusing examples:

By the time (that) this letter reaches you I will have left the country.

Can I use 'By the time (that) this letter reaches you I will leave the country' instead?

I've read the question about Future Simple and Future Perfect, but I still can't understand the exact usage of these two tenses.
Is there any diffrence between the following?

I will do my homework by 6 p.m.
I will have done my homework by 6 p.m.

I will do my homework after school
I will have done my homework after school

Also, I've checked the word 'by' in Oxford dictionary and there're some confusing examples:

By the time (that) this letter reaches you I will have left the country.

Can I use 'By the time (that) this letter reaches you I will leave the country' instead?

    Post Migrated Here from english.stackexchange.com
1
source | link

Future Simple and Future Perfect

I've read the question about Future Simple and Future Perfect, but I still can't understand the exact usage of these two tenses.
Is there any diffrence between the following?

I will do my homework by 6 p.m.
I will have done my homework by 6 p.m.

I will do my homework after school
I will have done my homework after school

Also, I've checked the word 'by' in Oxford dictionary and there're some confusing examples:

By the time (that) this letter reaches you I will have left the country.

Can I use 'By the time (that) this letter reaches you I will leave the country' instead?