diff --git a/doc/Extended-BASIC-TODO.md b/doc/Extended-BASIC-TODO.md
index 78194e9b..d262dbe9 100644
--- a/doc/Extended-BASIC-TODO.md
+++ b/doc/Extended-BASIC-TODO.md
@@ -58,6 +58,7 @@ Ideas for the future, most of them suitable for Mega65 or other power machines o
 * `RUN` should be able to run program from device, as in BASIC V10
 * `PAGE` and `DELAY` commands from Simons BASIC, or something similar
 * `DUMP` command from Simons BASIC, or something similar
+* it should be possbile to assign to `TI` special variable 
 * function to insert a substring starting from given position
 * function to generate string of n duplicated characters
 * function to retrieve fractional part of a number
diff --git a/src/basic/basic_commands/cmd_print.s b/src/basic/basic_commands/cmd_print.s
index c4c260c2..2dad7ba7 100644
--- a/src/basic/basic_commands/cmd_print.s
+++ b/src/basic/basic_commands/cmd_print.s
@@ -42,6 +42,8 @@ cmd_print_string:
 
 	// Print a string value
 
+	// XXX add optimized 46K/50K version
+
 	ldy #$00
 !:
 	cpy __FAC1 + 0
diff --git a/src/basic/engine_runtime/do_error.s b/src/basic/engine_runtime/do_error.s
index c8d51e0a..fc2b6573 100644
--- a/src/basic/engine_runtime/do_error.s
+++ b/src/basic/engine_runtime/do_error.s
@@ -182,9 +182,10 @@ do_basic_error:                        // error code in .X
 	jsr map_NORMAL
 #endif
 
-	// "?"
+	// Clear all temporary variables, print "?"
 	
 	phx_trash_a
+	jsr tmpstr_free_all
 	ldx #IDX__STR_RET_QM
 	jsr print_packed_misc_str
 	plx_trash_a
diff --git a/src/basic/engine_variables/assign_variable_TI_string.s b/src/basic/engine_variables/assign_variable_TI_string.s
index 46a2d09f..c18cbf1a 100644
--- a/src/basic/engine_variables/assign_variable_TI_string.s
+++ b/src/basic/engine_variables/assign_variable_TI_string.s
@@ -5,6 +5,80 @@
 
 assign_variable_TI_string:
 
-	// XXX implement
+	// Evaluate the expression, check if the result is suitable
 
-	jmp do_NOT_IMPLEMENTED_error
+	jsr FRMEVL
+
+	lda VALTYP
+	bpl_16 do_TYPE_MISMATCH_error      // branch if not string
+	
+	lda __FAC1+0
+	cmp #$06
+	bne_16 do_ILLEGAL_QUANTITY_error   // we need exactly 6-character string
+
+	// Initialize new time counter, process all the digits
+
+	ldy #$00
+
+	sty INDEX+0
+	sty INDEX+1
+	sty INDEX+2
+
+	// FALLTROUGH
+
+	// XXX provide optimized version for memory models 46K/50K
+
+assign_variable_TI_string_loop:
+
+	// First fetch the digit
+
+#if CONFIG_MEMORY_MODEL_60K
+	ldx #<(__FAC1 + 1)
+	jsr peek_under_roms
+#elif CONFIG_MEMORY_MODEL_46K || CONFIG_MEMORY_MODEL_50K
+	jsr peek_under_roms_via_FAC1_PLUS_1
+#else // CONFIG_MEMORY_MODEL_38K
+	lda (__FAC1 + 1), y
+#endif
+
+	jsr convert_PETSCII_to_digit
+	bcs_16 do_ILLEGAL_QUANTITY_error
+
+	tax                      // move decoded digit to .X
+
+	// Strangely, original implementation seems to be very permissive,
+	// it accepts any digit at any position; for compatibility
+	// we should better follow this convention
+
+assign_variable_TI_string_loop_digit:
+
+	cpx #$00
+	beq assign_variable_TI_string_loop_next
+
+	clc
+	lda table_TI_lo, y
+	adc INDEX+0
+	sta INDEX+0
+	lda table_TI_mid, y
+	adc INDEX+1
+	sta INDEX+1
+	lda table_TI_hi, y
+	adc INDEX+2
+	sta INDEX+2
+
+	dex
+	bpl assign_variable_TI_string_loop_digit     // branch always
+
+assign_variable_TI_string_loop_next:
+
+	iny
+	cpy #$06
+	bne assign_variable_TI_string_loop
+
+	// Set the resulting value
+
+	ldy INDEX+0
+	ldx INDEX+1
+	lda INDEX+2
+
+	jmp JSETTIM