Collect lines in a file

[sridhar]

Hi all,
If a line doesn't start with a timestamp , i need to add it with previous line through list.
this is the content of my file
9/16/16, 01:38 - User1: Hi , How you doing
9/16/16, 01:39 - User2: hi,
I'm good
How about you ?
Thanks for asking man
<media>
9/16/16, 02:02 - User3: Howdy folks!
9/16/16, 02:29 - User2: Awesome
9/16/16, 02:29 - User2: we are all good,
Thanks for asking
awesome
7/11/20, 13:00 - Me: <Video> watch this

Here is the code that I designed

intermediate =[]
finalData  = []
file = open('sample.txt', 'r' , encoding="utf8")
for lines in file:
    if startsWithDate(lines):
        intermediate .clear()
        intermediate .append(lines)
    else:
        intermediate .append(lines)
    intr = ' '.join(intermediate )
    finalData.append(intr)
print(finalData)

output obtained is

Output:
['9/16/16, 01:38 - User1: Hi , How you doing\n',
'9/16/16, 01:39 - User2: hi,\n',
"9/16/16, 01:39 - User2: hi,\n I'm good\n", 
"9/16/16, 01:39 - User2: hi,\n I'm good\n How about you ?\n",
"9/16/16, 01:39 - User2: hi,\n I'm good\n How about you ?\n Thanks for asking man\n", 
"9/16/16, 01:39 - User2: hi,\n I'm good\n How about you ?\n Thanks for asking man\n <media>\n", 
'9/16/16, 02:02 - User3: Howdy folks!\n', 
'9/16/16, 02:29 - User2: Awesome \n', 
'9/16/16, 02:29 - User2: we are all good,\n', 
'9/16/16, 02:29 - User2: we are all good,\n Thanks for asking\n', 
'9/16/16, 02:29 - User2: we are all good,\n Thanks for asking\n awesome\n',
'7/11/20, 13:00 - Me: <Video> watch this']

I don't need intermediate repeated outputs which are highlighted above.
Expected output is

Output:
['9/16/16, 01:38 - User1: Hi , How you doing\n',
"9/16/16, 01:39 - User2: hi,\n I'm good\n How about you ?\n Thanks for asking man\n <media>\n", 
'9/16/16, 02:02 - User3: Howdy folks!\n', 
'9/16/16, 02:29 - User2: Awesome \n', 
'9/16/16, 02:29 - User2: we are all good,\n Thanks for asking\n awesome\n', 
'7/11/20, 13:00 - Me: <Video> watch this']

Please help me out