定語從句時態由主句決定。籠統的說，主句是現在時，定從也是現在時；過去時也一樣。但如果定從中有些特別的時間狀語，定從會有些特別的時態。
你最好有具體的例題拿來，幫你分析。

I.
定義：定語是修飾名詞或代詞的成分,定語可由單詞、短語來充當。當用一個句子來充當名詞或代詞的修飾語時，這種起定語作用的句子就被稱為定語從句。
They
have
a
clever
son.
Do
you
know
the
man
over
there?
I
know
the
man
who
wrote
the
book.
II.
要點：
1．
定語從句的前面都有先行詞（被修飾語）
This
is
the
boy
whom
we
are
looking
for
2．
定語從句應緊跟在先行詞之后
3．
先行詞與定語從句之間要有關系詞（有時可省略）
4．
關系詞在定語從句中充當某一成分
The
girl
who
is
standing
under
the
tree
is
my
sister.
The
man
whom
you
want
to
see
has
come.
III.
關系詞基本用法
主格
賓格
所有格
人
who
whom
whose
物
which
which
of
which
但that
一般可用來代替who,
whom,
which,作賓格時可省略
Do
you
remember
the
teacher
that/who
taught
us
English?
A
bookstore
is
a
store
that/which
sells
books.
The
man
(that/whom/who)
you
know
is
a
famous
professor.
A)
that
不能用來替代who,
whom,
which的兩種情況
1）“介詞+whom/which”的結構中，不能用that
She
is
a
good
student
from
whom
we
should
learn.
2)
在非限制性定語從句中，逗號后面不能用that
She
sang
a
new
song,
which
we
like
very
much.
注意：非限制性定語從句的關系代詞不能省略
B)
用that不用which的一些特殊情況
1)
先行詞為all,
much,
little,
something,
anything,
everything,
nothing等
Is
there
anything
(that)
I
can
do
for
you?
2)
先行詞前有形容詞最高級修飾
This
is
the
most
exciting
report
that
I
have
ever
read.
3)
先行詞前有first,
last,
next,
only,
very,
all,
any等詞修飾
The
first
step
(that)
we
are
to
take
is
very
difficult.
4)
先行詞同時含有“人”和“非人”時，用that
不用which，也不用who/whom
He
talked
about
the
people
and
the
books
that
interested
him.
C)
關系副詞when,
where,
why
用關系副詞when時，它的先行詞是表示時間的名詞，用where時先行詞是表示地點的名詞，而用why時它的先行詞只可能是reason，使用時應注意以下幾點：
1）
關系代詞的選擇主要是看先行詞在從句中所作的成分
This
is
the
city
where
I
was
born.
This
is
the
city
(which/that)
he
has
visited
I
don’t
know
the
reason
why
she
is
late.
That
is
the
reason
(which/that)
everybody
knows
Do
you
still
remember
the
day
when
he
arrived?
Do
you
still
remember
the
day
(that/which)
we
spent
together?
2）
關系副詞when,where,
why可由“介詞+which”的結構來替代
Is
this
the
reason
for
which
they
came?
He
left
the
day
on
which
I
came.
注意：how
不能用來引導定語從句
This
is
the
way
how
he
did
it.
D)
As
作關系代詞的用法
與the
same,
such連用
This
is
the
same
book
as
I
read
last
week.
Such
books
as
I
have
read
are
classical
works.

根據實際情況選擇
He
is
the
man
that
I
met
last
night.
從句用了一般過去時，是因為，the
man
是
我昨天晚上遇到的
實際情況嘛

定語從句并沒有固定的時態規律。主從句時態都要根據具體情況而定。
eg. I will eat the food you bought yesterday. 主將從過去
I bought the same book this morning as you bought yesterday. 主過去，從過去。
I liked the way you spoke English, 主從都是一般過去時。
I have finished all the work that you asked me to do. 主句現在完成，從句一般過去。
I finished all the work that you had asked me to do. 主句一般過去， 從句過去完成。
沒有規律，沒有限制。主從句各自的時間狀語對應各自的時態。
希望能幫倒你。

主句是一般過去式，從句 一般 用過去完成時，例如I told mother that i had finished my homework.我完成作業發生在告訴媽媽之前，所以過去的過去應該用過去完成時；不過也有特殊的情況，例如Teacher told me that the moon goes around the earth when i was a pupil.當我還是個小學生的時候，老師就告訴過我月亮繞著地球轉。月亮繞著地球轉是客觀的科學事實，所以用了一般現在時態而不受主句的影響。同理，主句的一般現在時態也是這個道理了。

定語從句的時態一般和主句一致，但是如果從句描述的是個事實、一般規律，可以用一般現在時。本句的worries可以這樣解釋，如果是我寫的文章的話，我會用worried。